One boy wrote everything in JavaScript, and the client and the server said what he liked, convenient, readable. Then they took him to Durkee, of course.
- From the Internet

Content, or what we get at the output:

• Approaches

• Part One: Crutches

  
  
  • ECMAScript 5
  • ECMAScript 6
  • ECMAScript 6: Symbols
  • ECMAScript 6: Collections
  • ECMAScript 6: Iterators
  • ECMAScript 6: Promises
  • Mozilla JavaScript: Static Versions of Array Methods
  • Deferred execution: setTimeout, setInterval, setImmediate
  • Console
  
  

• Part Two: Bicycles

  
  
  • Data classification
  • Dictionaries
  • Partial application
  • Date formatting
  • Object API
  • Arrays
  • Numbers
  • Escaping special characters
  
  

• Conclusion

# Approaches

• The standard library should have all the minimum required for comfortable work, which does not include the ability to work with the API of a specific platform.
• Standards are our everything. The main part of the library is polyphiles. That's just not all the necessary functionality is standardized.
• If the functionality available in the system is implemented according to the specification or standard de facto, we leave the native one, but if the functionality is not standardized - in order to avoid conflicts in the future, we replace it by force.
• The library should be compact and well compressed.
• Modularity, the ability to collect only the necessary functionality.
• Write the final application - you are a king and god here and have the full right to use a library that extends native objects. The main thing is that only one library would do this.
• Write a library or npm module - you cannot use a library that extends native objects in any case. You risk condemning to conflicts programmer writing the final application. In this case there is the possibility of assembling without their expansion.

 console.log(Array.from(new Set([1, 2, 3, 2, 1]))); // => [1, 2, 3] console.log('*'.repeat(10)); // => '**********' Promise.resolve(32).then(console.log); // => 32 setImmediate(console.log, 42); // => 42 

 var log = core.console.log; log(core.Array.from(new core.Set([1, 2, 3, 2, 1]))); // => [1, 2, 3] log(core.String.repeat('*', 10)); // => '**********' core.Promise.resolve(32).then(log); // => 32 core.setImmediate(log, 42); // => 42 

 npm i core-js 

 //  : require('core-js'); //     : var core = require('core-js/library'); // ,   : require('core-js/shim'); 

• Maximum: development , production (21.8 kb without gzip)
• Without extension of native objects: development , production (21.8 kb without gzip)
• Only polyfiles: development , production (16.7 kb without gzip)

 npm i -g grunt-cli npm i core-js cd node_modules/core-js && npm i grunt build:date,console,library --path=custom uglify 

Part One: Crutches

# ECMAScript 5

# Array methods

 [1, 2, 3, 2, 1].indexOf(2); // => 1 [1, 2, 3, 2, 1].lastIndexOf(2); // => 3 [1, 2, 3].forEach(function(val, key){ console.log(val); // => 1, 2, 3 console.log(key); // => 0, 1, 2 }); [1, 2, 3].map(function(it){ return it * it; }); // => [1, 4, 9] [1, 2, 3].filter(function(it){ return it % 2; }); // => [1, 3] function isNum(it){ return typeof it == 'number'; } [1, '2', 3].every(isNum); // => false [1, '2', 3].some(isNum); // => true function add(a, b){ return a + b; } [1, 2, 3].reduce(add); // => 6 [1, 2, 3].reduceRight(add, ''); // => '321' 

 Array.prototype.map.call('123', function(it){ return it * it; }); // => [1, 4, 9] Array.prototype.slice.call('qwe', 1); // => ['w', 'e'] Array.prototype.join.call('qwe', '|'); // => 'q|w|e' 

 Array.isArray([1, 2, 3]); // => true Array.isArray(Object.create(Array.prototype)); // => false 

# Object API

 function Parent(/*...*/){ /*...*/ } Parent.prototype = {constructor: Parent /*, ... */} function Child(/*...*/){ Parent.call(this /*, ...*/); // ... } //   ES3 (  inherit  extend'): function Tmp(){} Tmp.prototype = Parent.prototype; Child.prototype = new Tmp; Child.prototype.constructor = Child; //   ES5: Child.prototype = Object.create(Parent.prototype, {constructor: {value: Child}}); var dict = Object.create(null); dict.key = 42; console.log(dict instanceof Object); // => false console.log(dict.toString) // => undefined console.log(dict.key) // => 42 

 var parent = {foo: 'bar'} , child = Object.create(parent); console.log(Object.getPrototypeOf(child) === parent); // => true function F(){} console.log(Object.getPrototypeOf(new F) === F.prototype); // => true F.prototype = {constructor: F /*, ...*/}; console.log(Object.getPrototypeOf(new F) === F.prototype); // => true F.prototype = {}; console.log(Object.getPrototypeOf(new F) === F.prototype); //  IE8-    

 console.log(Object.keys({q: 1, w: 2, e: 3})); // => ['q', 'w', 'e'] console.log(Object.keys([1, 2, 3])); // => ['0', '1', '2'] console.log(Object.getOwnPropertyNames([1, 2, 3])); // => ['0', '1', '2', 'length'] 

Object.freeze, Object.preventExtensions, Object.seal, with, eval
Crazy shit Stay away from it.
- Felix Geisendörfer

# Other

 var fn = console.log.bind(console, 42); fn(43); // => 42 43 

 Date.now(); // => 1400263401642 

 '\n  \n'.trim(); // => '' 

# ECMAScript 6

• Best of all, with its support for Firefox , a lot is already available.
• # In v8 (Chrome, Opera, Node.js) quite a lot is also available, but much of the features are blocked by default, to enable them in the browser, check the Enable experimental JavaScript box (the parser eats the chrome://flags/#enable-javascript-harmony link chrome://flags/#enable-javascript-harmony ), and Node.js to start with the --harmony . Something is available without a checkbox, for example, Promise , WeakMap and WeakSet , and starting with Chrome 38, Symbol , Map , Set , iterators are also available. Node.js lags far behind in this regard, since, especially in a stable branch, v8 is rarely updated there. But it, unlike the user's browser, no one will prevent you from launching with a flag.
• In IE , as usual, everything is bad, but the 11th version added collections and a couple more features. In the near future promise a lot .
• Add ES6 functionality tried in Safari . But almost everything that they added does not meet the standard and creates unnecessary problems, so it would be better not to add them. The link is only a small part of the problems.

# A little about ECMAScript 6+ preprocessors

# Object.assign

 var foo = {q: 1, w: 2} , bar = {e: 3, r: 4} , baz = {t: 5, y: 6}; Object.assign(foo, bar, baz); // => foo = {q: 1, w: 2, e: 3, r: 4, t: 5, y: 6} 

# Object.is

 NaN === NaN // => false 0 === -0 // => true,   : 1/0 === 1/-0 // => false 

 Object.is(NaN, NaN); // => true Object.is(0, -0); // => false Object.is(42, 42); // => true,  '===' Object.is(42, '42'); // => false,  '===' 

# Object.setPrototypeOf

 function Parent(){} function Child(){} Object.setPrototypeOf(Child.prototype, Parent.prototype); new Child instanceof Child; // => true new Child instanceof Parent; // => true function fn(){} Object.setPrototypeOf(fn, []); typeof fn == 'function'; // => true fn instanceof Array; // => true var object = {}; Object.setPrototypeOf(object, null); object instanceof Object; // => false 

 var setPrototypeOf = Function.call.bind(Object.getOwnPropertyDescriptor(Object.prototype, '__proto__').set); 

That's how we live:

• For IE10, emulation Object.setPrototypeOfis completely missing, since it is impossible.
• In older versions v8 Object.setPrototypeOfdoes not work, if the prototype chain of the target is absent Object.prototypeor property __proto__overridden through, for example Object.defineProperty.

# Array methods

 Array.from(new Set([1, 2, 3, 2, 1])); // => [1, 2, 3] Array.from({0: 1, 1: 2, 2: 3, length: 3}); // => [1, 2, 3] Array.from('123', Number); // => [1, 2, 3] Array.from('123', function(it){ return it * it; }); // => [1, 4, 9] 

 Array.of(1); // => [1] Array.of(1, 2, 3); // => [1, 2, 3] 

 function isOdd(val){ return val % 2; } [4, 8, 15, 16, 23, 42].find(isOdd); // => 15 [4, 8, 15, 16, 23, 42].findIndex(isOdd); // => 2 [4, 8, 15, 16, 23, 42].find(isNaN); // => undefined [4, 8, 15, 16, 23, 42].findIndex(isNaN); // => -1 

 Array(5).map(function(){ return 42; }); // => [undefined × 5],   .map  ""   Array(5).fill(42); // => [42, 42, 42, 42, 42] 

# String methods

 'foobarbaz'.includes('bar'); // => true 'foobarbaz'.includes('bar', 4); // => false 'foobarbaz'.startsWith('foo'); // => true 'foobarbaz'.startsWith('bar', 3); // => true 'foobarbaz'.endsWith('baz'); // => true 'foobarbaz'.endsWith('bar', 6); // => true 

 'string'.repeat(3); // => 'stringstringstring' 

# Working with numbers

# ECMAScript 6: Symbols

 var Person = (function(){ var NAME = Symbol('name'); function Person(name){ this[NAME] = name; } Person.prototype.getName = function(){ return this[NAME]; }; return Person; })(); var person = new Person(''); console.log(person.getName()); // => '' console.log(person['name']); // => undefined console.log(person[Symbol('name')]); // => undefined,   Symbol    for(var key in person)console.log(key); // =>  'getName',       console.log(typeof Symbol()); // => 'symbol' 

 window.Symbol || (function(){ var id = 0; window.Symbol = function(description){ if(this instanceof Symbol)throw new TypeError('Symbol is not a constructor'); var symbol = Object.create(Symbol.prototype) , tag = 'Symbol(' + description + ')_' + (++id + Math.random()).toString(36); symbol.tag = tag; Object.defineProperty(Object.prototype, tag, { configurable: true, set: function(it){ Object.defineProperty(this, tag, { enumerable : false, configurable: true, writable : true, value : it }); } }); return symbol; } Symbol.prototype.toString = function(){ return this.tag; } })(); 

• Writes a setter in Object.prototype: Do not particularly abuse, may affect performance.
• : IE8- ( # Object.defineProperty ), Object.prototype , «» .
• , Object.prototype (, Object.create(null) ), «» .
• Symbol() in {} true — .
• typeof Symbol() 'object' — JavaScript .
• Object.getOwnPropertySymbols — Object.getOwnPropertyNames , , Object.getOwnPropertyNames , , «».

 var Person = function(){ var NAME = Symbol.pure('name'); function Person(name){ Symbol.set(this, NAME, name); } Person.prototype.getName = function(){ return this[NAME]; }; return Person; }(); 

 var O = {a: 1}; Object.defineProperty(O, 'b', {value: 2}); O[Symbol('c')] = 3; Reflect.ownKeys(O); // => ['a', 'b', Symbol(c)] 

 var symbol = Symbol.for('key'); symbol === Symbol.for('key'); // true Symbol.keyFor(symbol); // 'key' 

# ECMAScript 6: Collections

• # Description of collections
• # Support for engines
• # Implementation MapandSet
• # Implementation of loosely coupled collections

 var a = [1]; var map = new Map([['a', 1], [42, 2]]); map.set(a, 3).set(true, 4); console.log(map.size); // => 4 console.log(map.has(a)); // => true console.log(map.has([1])); // => false console.log(map.get(a)); // => 3 map.forEach(function(val, key){ console.log(val); // => 1, 2, 3, 4 console.log(key); // => 'a', 42, [1], true }); map.delete(a); console.log(map.size); // => 3 console.log(map.get(a)); // => undefined console.log(Array.from(map)); // => [['a', 1], [42, 2], [true, 4]] 

 var set = new Set(['a', 'b', 'a', 'c']); set.add('d').add('b').add('e'); console.log(set.size); // => 5 console.log(set.has('b')); // => true set.forEach(function(it){ console.log(it); // => 'a', 'b', 'c', 'd', 'e' }); set.delete('b'); console.log(set.size); // => 4 console.log(set.has('b')); // => false console.log(Array.from(set)); // => ['a', 'c', 'd', 'e'] 

 var a = [1] , b = [2] , c = [3]; var wmap = new WeakMap([[a, 1], [b, 2]]); wmap.set(c, 3).set(b, 4); console.log(wmap.has(a)); // => true console.log(wmap.has([1])); // => false console.log(wmap.get(a)); // => 1 wmap.delete(a); console.log(wmap.get(a)); // => undefined //      var Person = (function(){ var names = new WeakMap; function Person(name){ names.set(this, name); } Person.prototype.getName = function(){ return names.get(this); }; return Person; })(); var person = new Person(''); console.log(person.getName()); // => '' for(var key in person)console.log(key); // =>  'getName' 

 var a = [1] , b = [2] , c = [3]; var wset = new WeakSet([a, b, a]); wset.add(c).add(b).add(c); console.log(wset.has(b)); // => true console.log(wset.has([2])); // => false wset.delete(b); console.log(wset.has(b)); // => false 

• In Firefox there is full Map, Setand WeakMap. In the nightly assemblies appeared and WeakSet. Mapand Settake the object being iterated. Mapand Sethave iterators and a method .forEach.
• v8 — Chrome, Opera Node.js , 4 . Chrome 38, . WeakMap WeakSet . # . v8 , Map Set .forEach , Map Set , .
• IE11 Map, Set WeakMap . . Map Set , .forEach .
• Safari , . Map, Set WeakMap . . , , , , , next . forEach , 3 , , 1 Set 2 Map .

# Implementation of Map and Set

 var array = []; for(var i = 0; i < 100000; i++)array.push([{}, {}]); array = array.concat(array); console.time('Map test'); var map = new Map(array); console.timeEnd('Map test'); console.log('Map size: ' + map.size); 

 Map test:   Map test: 46.25 Map size: 100000 

 Map test:   Map test: 506823.31 Map size: 100000 

 function fastKey(key){ if(typeof key === 'string')return '$' + key; else if(typeof key === 'number')return key; return null; }; 

 var STOREID = Symbol('storeId') , id = 0; function fastKey(it){ //    'S'      'P'    if(it !== Object(it))return (typeof it == 'string' ? 'S' : 'P') + it; //      -  if(!Object.hasOwnProperty.call(it, STOREID))it[STOREID] = ++id; //     'O' return 'O' + it[STOREID]; } 

 Map test:   Map test: 669.93 Map size: 100000 

#

 window.WeakMap || (function(){ var id = 0 , has = Function.call.bind(Object.prototype.hasOwnProperty) , WEAKDATA = Symbol('WeakData') , ID = Symbol('ID'); window.WeakMap = function(){ if(!(this instanceof WeakMap))throw TypeError(); this[ID] = id++; } Object.assign(WeakMap.prototype, { 'delete': function(key){ return this.has(key) && delete key[WEAKDATA][this[ID]]; }, has: function(key){ return key === Object(key) && has(key, WEAKDATA) && has(key[WEAKDATA], this[ID]); }, get: function(key){ if(key === Object(key) && has(key, WEAKDATA))return key[WEAKDATA][this[ID]]; }, set: function(key, value){ if(key !== Object(key))throw TypeError(); if(!has(key, WEAKDATA))key[WEAKDATA] = {}; key[WEAKDATA][this[ID]] = value; return this; } }); })(); 

 // <-   snapshot 1 var array = []; for(var i = 0; i < 100000; i++)array[i] = {}; var wm = new WeakMap(); for(var i = 0; i < 100000; i++)wm.set(array[i], {}); // <-   snapshot 2 array = null; // <-   snapshot 3 

# ECMAScript 6: Iterators

• # Iterator interface
• # Interface of the object being iterated, symbol Symbol.iterator
• # Generators
• # Cycle for-of
• # Iterators of instances of built-in constructors and methods that return them
• # Methods and constructors taking iterable objects
• # Operator spread
• # Array / generator comprehensions

 function NumberIterator(number){ var i = 0; return { next: function(){ return i < number ? {done: false, value: i++} : {done: true}; } } } var iter = NumberIterator(3); iter.next(); // => {done: false, value: 0} iter.next(); // => {done: false, value: 1} iter.next(); // => {done: false, value: 2} iter.next(); // => {done: true} 

 Number.prototype[Symbol.iterator] = function(){ return NumberIterator(this); } Array.from(10); // => [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] 

 Number.prototype[Symbol.iterator] = function*(){ for(var i = 0; i < this;)yield i++; } Array.from(10); // => [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] 

 for(var num of 5)console.log(num); // => 0, 1, 2, 3, 4 

 var string = 'abc'; for(var val of string)console.log(val); // => 'a', 'b', 'c' var array = ['a', 'b', 'c']; for(var val of array)console.log(val); // => 'a', 'b', 'c'.    - .values for(var val of array.values())console.log(val); // => 'a', 'b', 'c' for(var key of array.keys())console.log(key); // => 0, 1, 2 for(var [key, val] of array.entries()){ console.log(key); // => 0, 1, 2 console.log(val); // => 'a', 'b', 'c' } var map = new Map([['a', 1], ['b', 2], ['c', 3]]); for(var [key, val] of map){ //    - .entries console.log(key); // => 'a', 'b', 'c' console.log(val); // => 1, 2, 3 } for(var val of map.values())console.log(val); // => 1, 2, 3 for(var key of map.keys())console.log(key); // => 'a', 'b', 'c' for(var [key, val] of map.entries()){ console.log(key); // => 'a', 'b', 'c' console.log(val); // => 1, 2, 3 } var set = new Set([1, 2, 3, 2, 1]); for(var val of set)console.log(val); // => 1, 2, 3.    - .values for(var val of set.values())console.log(val); // => 1, 2, 3 for(var key of set.keys())console.log(key); // => 1, 2, 3.  .keys  .values for(var [key, val] of set.entries()){ //  Set   .entries     console.log(key); // => 1, 2, 3 console.log(val); // => 1, 2, 3 } var list = (function(){return arguments})(1, 2, 3); for(var val of list)console.log(val); // => 1, 2, 3 

• The current Firefox has all of these iterators, except the iterator arguments. The cycle works, but on the basis of its own, outdated, protocol.
• In v8, the loop for-of, starting with Chrome 38, works correctly (not counting the destruction of the array) and all of these iterators are available, except arguments. In older versions (with a checkbox), an iterator was expected, not an iterated object.
• IE, , .

 $for(new Set([1, 2, 3, 2, 1])).of(function(it){ console.log(it); // => 1, 2, 3 }); // 2  $for -  entries -    2  $for([1, 2, 3].entries(), true).of(function(key, value){ console.log(key); // => 0, 1, 2 console.log(value); // => 1, 2, 3 }); // 2  .of -    $for('abc').of(console.log, console); // => 'a', 'b', 'c' //    ,    false $for([1, 2, 3, 4, 5]).of(function(it){ console.log(it); // => 1, 2, 3 if(it == 3)return false; }); 

 var list = (function(){return arguments})(1, 2, 3); console.log($for.isIterable(list)); // => true console.log($for.isIterable({})); // => false var iter = $for.getIterator(list); console.log(iter.next()); // => {value: 1, done: false} console.log(iter.next()); // => {value: 2, done: false} console.log(iter.next()); // => {value: 3, done: false} console.log(iter.next()); // => {value: undefined, done: true} 

 [...new Set([1, 2, 3, 2, 1])]; // => [1, 2, 3] console.log(1, ...[2, 3, 4]); // => 1, 2, 3, 4 var map = new Map([[1, 'a'], [2, 'b']]); new Array(...map.keys(), 3); // => [1, 2, 3] 

 var ar1 = [for(i of [1, 2, 3])i * i]; // => [1, 4, 9] var set = new Set([1, 2, 3, 2, 1]); var ar2 = [for(i of set)if(i % 2)i * i]; // => [1, 9] var iter = (for(i of set)if(i % 2)i * i); iter.next(); // => {value: 1, done: false} iter.next(); // => {value: 9, done: false} iter.next(); // => {value: undefined, done: true} var map1 = new Map([['a', 1], ['b', 2], ['c', 3]]); var map2 = new Map((for([k, v] of map1)if(v % 2)[k + k, v * v])); // => Map {aa: 1, cc: 9} 

 var ar1 = $for([1, 2, 3]).array(function(v){ return v * v; }); // => [1, 4, 9] var set = new Set([1, 2, 3, 2, 1]); var ar1 = $for(set).filter(function(v){ return v % 2; }).array(function(v){ return v * v; }); // => [1, 9] var iter = $for(set).filter(function(v){ return v % 2; }).map(function(v){ return v * v; }); iter.next(); // => {value: 1, done: false} iter.next(); // => {value: 9, done: false} iter.next(); // => {value: undefined, done: true} var map1 = new Map([['a', 1], ['b', 2], ['c', 3]]); var map2 = new Map($for(map1, true).filter(function(k, v){ return v % 2; }).map(function(k, v){ return [k + k, v * v]; })); // => Map {aa: 1, cc: 9} 

# ECMAScript 6: Promises

 var log = console.log.bind(console); function sleepRandom(time){ return new Promise(function(resolve, reject){ // resolve   , reject -   //      setTimeout(resolve, time * 1e3, 0 | Math.random() * 1e3); }); } log(''); // =>  sleepRandom(5).then(function(result){ log(result); // => 869,  5 . return sleepRandom(10); }).then(function(result){ log(result); // => 202,  10 . }).then(function(){ log('  '); // =>    throw Error('!'); }).then(function(){ log('   - '); }).catch(log); // => Error: '!' 

 Promise.resolve(42).then(log); // => 42 Promise.reject(42).catch(log); // => 42 Promise.resolve($.getJSON('/data.json')); // => ES6 promise 

 Promise.all([ 'foo', sleepRandom(5), sleepRandom(15), sleepRandom(10) //  15   -  ]).then(log); // => ['foo', 956, 85, 382] 

 function timeLimit(promise, time){ return Promise.race([promise, new Promise(function(resolve, reject){ setTimeout(reject, time * 1e3, Error('Await > ' + time + ' sec')); })]); } timeLimit(sleepRandom(5), 10).then(log); // =>  5    853 timeLimit(sleepRandom(15), 10).catch(log); // Error: Await > 10 sec 

 var delay = time => new Promise(resolve => setTimeout(resolve, time)); async function sleepRandom(time){ await delay(time * 1e3); return 0 | Math.random() * 1e3; } async function sleepError(time, msg){ await delay(time * 1e3); throw Error(msg); } (async () => { try { log(''); // =>  log(await sleepRandom(5)); // => 936,  5 . var [a, b, c] = await Promise.all([ sleepRandom(5), sleepRandom(15), sleepRandom(10) ]); log(a, b, c); // => 210 445 71,  15 . await sleepError(5, '!'); log('  '); } catch(e){ log(e); // => Error: '!',  5 . } })(); 

# Mozilla JavaScript: Static Versions of Array Methods

 Array.prototype.slice.call(arguments, 1); //  [].slice.call(arguments, 1); 

 Array.from(arguments).slice(1); 

 Array.slice(arguments, 1); Array.join('abcdef', '+'); // => 'a+b+c+d+e+f' var form = document.getElementsByClassName('form__input'); Array.reduce(form, function(memo, it){ memo[it.name] = it.value; return memo; }, {}); // => , {name: '', age: '42', sex: 'yes, please'} 

# Deferred execution: setTimeout, setInterval, setImmediate

# setTimeout, setInterval

 // : setTimeout(log.bind(null, 42), 1000); // : setTimeout(log, 1000, 42); 

# setImmediate

• For older versions of Node.js - process.nextTick
• For modern browsers - postMessage
• For WebWorkers - MessageChannel
• For IE8- - script.onreadystatechange
• And even if these methods did not help - setTimeoutwith minimal delay

 setImmediate(function(arg1, arg2){ console.log(arg1, arg2); // =>        }, '   ', '  '); clearImmediate(setImmediate(function(){ console.log('   '); })); 

# Console

 // : if(window.console && console.log)console.log(42); // : console.log(42); 

 // : setTimeout(console.log.bind(console, 42), 1000); [1, 2, 3].forEach(console.log, console); // : setTimeout(console.log, 1000, 42); [1, 2, 3].forEach(console.log); 

Since the console is not standardized, add a little ad-lib:

 console.disable(); console.warn(' ,     .'); console.enable(); console.warn('  .'); 

# Part Two: Bicycles

Options zero, no options.
I wanted half the world - enough for a bike.
- Loop of addiction

# Classification of data

 Object.isObject = function(it){ return it != null && (typeof it == 'object' || typeof it == 'function'); } // ... typeof {}; // => 'object' typeof isNaN; // => 'function' typeof null; // => 'object' Object.isObject({}); // => true Object.isObject(isNaN); // => true Object.isObject(null); // => false 

 Object.prototype.toString.call(1).slice(8, -1); // => 'Number' Object.prototype.toString.call([]).slice(8, -1); // => 'Array' Object.prototype.toString.call(/./).slice(8, -1); // => 'RegExp' 

• In older IE, applicable to null, undefinedand arguments, this construct returns "Object". This is easily treated with additional checks.
• ECMAScript 6, ? "Object" . Object#toString ECMAScript 6.

 var classof = Object.classof; classof(null); // => 'Null' classof(undefined); // => 'Undefined' classof(1); // => 'Number' classof(true); // => 'Boolean' classof('string'); // => 'String' classof(Symbol()); // => 'Symbol' classof(new Number(1)); // => 'Number' classof(new Boolean(true)); // => 'Boolean' classof(new String('string')); // => 'String' var fn = function(){} , list = (function(){return arguments})(1, 2, 3); classof({}); // => 'Object' classof(fn); // => 'Function' classof([]); // => 'Array' classof(list); // => 'Arguments' classof(/./); // => 'RegExp' classof(new TypeError); // => 'Error' classof(new Set); // => 'Set' classof(new Map); // => 'Map' classof(new WeakSet); // => 'WeakSet' classof(new WeakMap); // => 'WeakMap' classof(new Promise(fn)); // => 'Promise' classof([].values()); // => 'Array Iterator' classof(new Set().values()); // => 'Set Iterator' classof(new Map().values()); // => 'Map Iterator' classof(Math); // => 'Math' classof(JSON); // => 'JSON' function Example(){} Example.prototype[Symbol.toStringTag] = 'Example'; classof(new Example); // => 'Example' 

# Dictionaries

• # Problem: Object.prototypeand dictionaries
• # Constructor Dict
• # Methods for safe work with a dictionary that has a prototype
• # Methods for working with a dictionary
• # Iteration through the dictionary
• Possible prospects

# Problem: Object.prototype and dictionaries

 Object.prototype.constructor(); Object.prototype.hasOwnProperty(); Object.prototype.isPrototypeOf(); Object.prototype.propertyIsEnumerable(); Object.prototype.toLocaleString(); Object.prototype.toString(); Object.prototype.valueOf(); Object.prototype.__proto__; Object.prototype.__count__; Object.prototype.__parent__; Object.prototype.__noSuchMethod__; Object.prototype.__defineGetter__(); Object.prototype.__defineSetter__(); Object.prototype.__lookupGetter__(); Object.prototype.__lookupSetter__(); Object.prototype.eval(); Object.prototype.toSource(); Object.prototype.unwatch(); Object.prototype.watch(); 

 var phone = (function(){ var db = { '': '+7987654', '': '+7654321' }; return { has: function(name){ return name in db; }, get: function(name){ return db[name]; }, set: function(name, phone){ db[name] = phone; }, delete: function(name){ delete db[name]; } }; })(); 

 console.log(phone.has('')); // => true console.log(phone.get('')); // => '+7987654' console.log(phone.has('')); // => false console.log(phone.get('')); // => undefined console.log(phone.has('toString')); // => true console.log(phone.get('toString')); // => function toString() { [native code] } 

 // ... has: function(name){ return db.hasOwnProperty(name); }, get: function(name){ if(db.hasOwnProperty(name))return db[name]; }, // ... console.log(phone.get('')); // => '+7987654' phone.set('hasOwnProperty', '+7666666'); //   "" console.log(phone.get('')); // TypeError: string is not a function 

 // ... has: function(name){ return Object.prototype.hasOwnProperty.call(db, name); }, get: function(name){ if(Object.prototype.hasOwnProperty.call(db, name))return db[name]; }, // ... 

 phone.set('__proto__', '+7666666'); //   "" console.log(phone.get('__proto__')); // => undefined 

 // ... set: function(name, phone){ Object.defineProperty(db, name, { enumerable : true, configurable: true, writable : true, value : phone }); }, // ... 

 var phone = (function(){ var db = Object.create(null); Object.assign(db, { '': '+7987654', '': '+7654321' }); return { has: function(name){ return name in db; }, get: function(name){ return db[name]; }, set: function(name, phone){ db[name] = phone; }, delete: function(name){ delete db[name]; } }; })(); 

• It will not be possible to result in a number, for example +Object.create(null), or the string,, '' + Object.create(null)-TypeError
• Accordingly, it will not be possible to compare the object with an abstract equality algorithm, for example ==, with primitives -TypeError

# ConstructorDict

 function Dict(props){ var dict = Object.create(null); if(props != null){ if(Symbol.iterator in props){ for(var [key, val] of props)dict[key] = val; } else Object.assign(dict, props); } return dict; } Dict.prototype = null; Dict.isDict = function(it){ return Object.isObject(it) && Object.getPrototypeOf(it) === null; } // ... var map = new Map([['a', 1], ['b', 2], ['c', 3]]); Dict(); // => {__proto__: null} Dict({a: 1, b: 2, c: 3}); // => {__proto__: null, a: 1, b: 2, c: 3} Dict(map); // => {__proto__: null, a: 1, b: 2, c: 3} Dict([1, 2, 3].entries()); // => {__proto__: null, 0: 1, 1: 2, 2: 3} Dict((for([k, v] of map)if(v % 2)[k + k, v * v])); // => {__proto__: null, aa: 1, cc: 9} Dict.isDict({}); // => false Dict.isDict(Dict()); // => true 

# Methods for safe work with a dictionary that has a prototype

 var dict = {a: 1, b: 2, c: 3}; console.log(Dict.has(dict, 'a')); // => true console.log(Dict.has(dict, 'toString')); // => false console.log(Dict.get(dict, 'a')); // => 1 console.log(Dict.get(dict, 'toString')); // => undefined Dict.set(dict, '__proto__', 42); console.log(Dict.get(dict, '__proto__')); // => 42 

# Methods for working with a dictionary

 var dict = {a: 1, b: 2, c: 3}; Dict.forEach(dict, console.log, console); // => 1, 'a', {a: 1, b: 2, c: 3} // => 2, 'b', {a: 1, b: 2, c: 3} // => 3, 'c', {a: 1, b: 2, c: 3} Dict.map(dict, function(it){ return it * it; }); // => {a: 1, b: 4, c: 9} Dict.filter(dict, function(it){ return it % 2; }); // => {a: 1, c: 3} Dict.some(dict, function(it){ return it === 2; }); // => true Dict.every(dict, function(it){ return it === 2; }); // => false Dict.find(dict, function(it){ return it > 2; }); // => 3 Dict.find(dict, function(it){ return it > 4; }); // => undefined Dict.findKey(dict, function(it){ return it > 2; }); // => 'c' Dict.findKey(dict, function(it){ return it > 4; }); // => undefined Dict.keyOf(dict, 2); // => 'b' Dict.keyOf(dict, 4); // => undefined Dict.includes(dict, 2); // => true Dict.includes(dict, 4); // => false Dict.reduce(dict, function(memo, it){ return memo + it; }); // => 6 Dict.reduce(dict, function(memo, it){ return memo + it; }, ''); // => '123' Dict.turn(dict, function(memo, it, key){ memo[key + key] = it; }); // => {aa: 1, bb: 2, cc: 3} Dict.turn(dict, function(memo, it, key){ it % 2 && memo.push(key + it); }, []); // => ['a1', 'c3'] 

# Iteration through the dictionary

 var dict = {a: 1, b: 2, c: 3}; console.log(Object.values(dict)); // => [1, 2, 3] console.log(Object.entries(dict)); // => [['a', 1], ['b', 2], ['c', 3]] for(var key of Dict.keys(dict))console.log(key); // => 'a', 'b', 'c' for(var [key, val] of Dict.entries(dict)){ console.log(key); // => 'a', 'b', 'c' console.log(val); // => 1, 2, 3 } $for(Dict.values(dict)).of(console.log); // => 1, 2, 3 new Map(Dict.entries(dict)); // => Map {a: 1, b: 2, c: 3} new Map((for([k, v] of Dict.entries(dict))if(v % 2)[k + k, v * v])); // => Map {aa: 1, cc: 9} 

# Possible perspectives

 function Dict(props){ if(!(this instanceof Dict))return new Dict(props); if(props != null){ if(Symbol.iterator in props){ for(var [key, val] of props)this[key] = val; } else Object.assign(this, props); } } Dict.prototype = Object.create(null); Dict.prototype[Symbol.toStringTag] = 'Dict'; Dict.prototype[Symbol.iterator] = function(){ return Dict.entries(this); }; 

• new Dict instanceof Dict .
• for(var [key, value] of dict){...}, new Map(dict)without having to get an iterator through Dict.entries.
• #Object.classof(new Dict) would return 'Dict', not 'Object'.

# Partial application

• # Partial application without context binding
• # Partial application of arbitrary arguments
• # Extract method from object
• # Limiting the number of arguments

# Partial application without context binding

 Array.prototype.compact = [].filter.bind(Array.prototype, function(val){ return val != null; }); [0, null, 1, undefined, 2].compact(); // => [] -     Array.prototype,     //    : Array.prototype.compact = function(){ return this.filter(function(val){ return val != null; }); }; [0, null, 1, undefined, 2].compact(); // => [0, 1, 2]; 

 Array.prototype.compact = [].filter.part(function(val){ return val != null; }); [0, null, 1, undefined, 2].compact(); // => [0, 1, 2]; var fn = console.log.part(1, 2); fn(3, 4); // => 1, 2, 3, 4 

# Partial application of arbitrary arguments

 function fn1(a, c){ console.log(a, 2, c, 4); }; fn1(1, 3); // => 1, 2, 3, 4 function fn2(b, c){ console.log(1, b, c, 4); }; fn2(2, 3); // => 1, 2, 3, 4 

 var fn1 = console.log.part(_, 2, _, 4); fn1(1, 3); // => 1, 2, 3, 4 var fn2 = console.log.part(1, _, _, 4); fn2(2, 3); // => 1, 2, 3, 4 fn1(1, 3, 5); // => 1, 2, 3, 4, 5 fn1(1); // => 1, 2, undefined, 4 

 var fn = console.log.by(console, _, 2, _, 4); fn(1, 3, 5); // => 1, 2, 3, 4, 5 

# Extract method from object

 ['foobar', 'foobaz', 'barbaz'].filter(/bar/[_]('test')); // => ['foobar', 'barbaz'] var has = {}.hasOwnProperty[_]('call'); console.log(has({key: 42}, 'foo')); // => false console.log(has({key: 42}, 'key')); // => true var array = [] , push = array[_]('push'); push(1); push(2, 3); console.log(array); // => [1, 2, 3]; 

 var _ = Symbol(); Object.defineProperty(Object.prototype, _, { get: function(){ return new Proxy(this, { apply: function(){ /*    [_]    */ }, get: function(context, name){ return context[name].bind(context); } }); } }); ['foobar', 'foobaz', 'barbaz'].filter(/bar/[_].test); // => ['foobar', 'barbaz'] var has = {}.hasOwnProperty[_].call; console.log(has({key: 42}, 'foo')); // => false console.log(has({key: 42}, 'key')); // => true var array = [] , push = array[_].push; push(1); push(2, 3); console.log(array); // => [1, 2, 3]; 

#

 [1, 2, 3].forEach(console.log); // => 1 0 [1, 2, 3] // => 2 1 [1, 2, 3] // => 3 2 [1, 2, 3] 

 [1, 2, 3].forEach(function(it){ console.log(it); }); // => 1, 2, 3 

 [1, 2, 3].forEach(console.log.only(1)); // => 1, 2, 3 

# Date formatting

 var date = new Date; function lz2(it){ return it > 9 ? it : '0' + it; } var format = [date.getDate(), date.getMonth() + 1, date.getFullYear()].map(lz2).join('.') + ' ' + [date.getHours(), date.getMinutes(), date.getSeconds()].map(lz2).join(':'); console.log(format); // => '18.11.2014 06:07:25 ' 

 new Date().toLocaleString('ru-RU', { weekday: 'long', year: 'numeric', month: 'long', day: 'numeric', hour: 'numeric', minute: '2-digit', second: '2-digit' }); // => ', 18  2014 ., 6:07:25' 

# Add a simple date formatting.

 new Date().format('W, D MM Y ., h:mm:ss', 'ru'); // => ', 18  2014 ., 6:07:25' new Date().formatUTC('W, D MM Y ., h:mm:ss', 'ru'); // => ', 18  2014 ., 0:07:25' 

 s |  | 0-59 ss | , 2  | 00-59 m |  | 0-59 mm | , 2  | 00-59 h |  | 0-23 hh | , 2  | 00-23 D |  | 1-31 DD | , 2  | 01-31 W |  ,  |  N |  | 1-12 NN | , 2  | 01-12 M | ,  |  MM | ,  |  Y | ,  | 2014 YY | , 2  | 14 

 new Date().format('W, D MM Y', 'ru'); // => ', 18  2014' new Date().format('W, D MM Y'); // => 'Tuesday, 18 November 2014' core.locale('ru'); new Date().format('W, D MM Y'); // => ', 18  2014' 

 (typeof core != 'undefined' ? core : require('core-js/library')).addLocale('ru', { weekdays: ',,,,,,', months: ':|,:|,:|,:|,:|,:|,:|,:|,:|,:|,:|,:|' }); 

 new Date().format('DD.NN.YY'); // => '18.11.14' new Date().format('hh:mm:ss'); // => '06:07:25' new Date().format('DD.NN.Y hh:mm:ss'); // => '18.11.2014 06:07:25' new Date().format('W, D MM Y '); // => ', 18  2014 ' new Date().format('D MM, h:mm'); // => '18 , 6:07' new Date().format('M Y'); // => ' 2014' 

# Object API

 // : Object.defineProperty(target, 'c', { enumerable: true, configurable: true, get: function(){ return this.a + this.b; } }); // : Object.define(target, { get c(){ return this.a + this.b; } }); 

 //        : var copy = Object.make(Object.getPrototypeOf(src), src); //   : function Vector2D(x, y){ this.x = x; this.y = y; } Object.define(Vector2D.prototype, { get xy(){ return Math.hypot(this.x, this.y); } }); function Vector3D(x, y, z){ Vector2D.apply(this, arguments); this.z = z; } Vector3D.prototype = Object.make(Vector2D.prototype, { constructor: Vector3D, get xyz(){ return Math.hypot(this.x, this.y, this.z); } }); var vector = new Vector3D(9, 12, 20); console.log(vector.xy); // => 15 console.log(vector.xyz); // => 25 vector.y++; console.log(vector.xy); // => 15.811388300841896 console.log(vector.xyz); // => 25.495097567963924 

# Arrays

 [1, 2, 3].includes(2); // => true [1, 2, 3].includes(4); // => false [1, 2, 3].includes(2, 2); // => false [NaN].indexOf(NaN); // => -1 [NaN].includes(NaN); // => true Array(1).indexOf(undefined); // => -1 Array(1).includes(undefined); // => true 

 //   : [1, 2, 3, 4, 5].reduce(function(memo, it){ memo['key' + it] = !!(it % 2); return memo; }, {}); // => {key1: true, key2: false, key3: true, key4: false, key5: true} [1, 2, 3, 4, 5].turn(function(memo, it){ memo['key' + it] = !!(it % 2); }, {}); // => {key1: true, key2: false, key3: true, key4: false, key5: true} // filter + map + slice,   : [1, 2, 3, 4, 5, 6, 7, 8, 9].map(function(it){ return it * it; }).filter(function(it){ return it % 2; }).slice(0, 2); // => [1, 9] [1, 2, 3, 4, 5, 6, 7, 8, 9].turn(function(memo, it){ it % 2 && memo.push(it * it); if(memo.length == 2)return false; }); // => [1, 9] 

# Numbers

 //  : for(var i = 0; i < 3; i++)console.log(i); // => 0, 1, 2 // for-of   : for(var i of 3)console.log(i); // => 0, 1, 2 //   for-of, : $for(3).of(console.log); // => 0, 1, 2 //    : // .map  ""   Array(10).map(Math.random); // => [undefined × 10] // ES5 ,   : Array.apply(undefined, Array(10)).map(Math.random); // => [0.9442228835541755, 0.8101077508181334, ...] // ES6 ,   : Array(10).fill(undefined).map(Math.random); // => [0.5587614295072854, 0.009569905698299408, ...] // Number Iterator: Array.from(10, Math.random); // => [0.9817775336559862, 0.02720663254149258, ...] Array.from(10); // => [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] Array.from(10, function(it){ return this + it * it; }, .42); // => [0.42, 1.42, 4.42, 9.42, 16.42, 25.42, 36.42, 49.42, 64.42, 81.42] // Comprehensions: [for(i of 10)if(i % 2)i * i]; // => [1, 9, 25, 49, 81] Dict((for(i of 3)['key' + i, !(i % 2)])); // => {key0: true, key1: false, key2: true} $for(10).filter(function(i){ return i % 2; }).array(function(i){ return i * i; }); // => [1, 9, 25, 49, 81] Dict($for(3).map(function(i){ return ['key' + i, !(i % 2)]; })); // => {key0: true, key1: false, key2: true} 

 3..pow(3); // => 27 (-729).abs().sqrt(); // => 27 10..random(20); // =>   (10, 20), , 16.818793776910752 10..random(20).floor(); // =>   [10, 19], , 16 var array = [1, 2, 3, 4, 5]; array[array.length.random().floor()]; // =>   , , 4 

# Escaping special characters

 '<script>doSomething();</script>'.escapeHTML(); // => '&lt;script&gt;doSomething();&lt;/script&gt;' '&lt;script&gt;doSomething();&lt;/script&gt;'.unescapeHTML(); // => '<script>doSomething();</script>' 

 RegExp.escape(' -[]{}()*+?.,\\^$|'); // => ' \-\[\]\{\}\(\)\*\+\?\.\,\\\^\$\|' 

# Conclusion