Underscore Parsing

In this post, a javascript lover, armed with a chainsaw, mercilessly saws one of the best, in his opinion, universal libraries.



We prepare this source from the point of view of the pupil of the 5th “B” Vasi Pupkin, who has read a book on the basics of javascript, and is eager to get better at entangling in the knowledge gained.

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Initial cutting

• module creation or 'universal blank'
  
  code

  (function() { //    (window  exports)    var root = this; //   underscore,      . var previousUnderscore = root._; //      if (typeof exports !== 'undefined') { if (typeof module !== 'undefined' && module.exports) { exports = module.exports = _; } exports._ = _; } else { root._ = _; } //         _.noConflict = function() { root._ = previousUnderscore; return this; }; // ,         if (typeof define === 'function' && define.amd) { define('underscore', [], function() { return _; }); } }.call(this)); //      

  
  
• initial _ (something that can be used like this _. function (something) or so _ (something). function ()
  
  code

    //       -     -     . var _ = function(obj) { if (obj instanceof _) return obj; if (!(this instanceof _)) return new _(obj); this._wrapped = obj; }; 

  
  
• creating short links
  
  code

    var ArrayProto = Array.prototype, ObjProto = Object.prototype, FuncProto = Function.prototype; //       var push = ArrayProto.push, slice = ArrayProto.slice, concat = ArrayProto.concat, toString = ObjProto.toString, hasOwnProperty = ObjProto.hasOwnProperty; //      var nativeIsArray = Array.isArray, nativeKeys = Object.keys, nativeBind = FuncProto.bind; 

  
  
• additive version
  
  code

    _.VERSION = '1.7.0'; 

  
  
• creating a function that is used on each element, inside other functions that iterate over the elements
  
  code

    //         , //   this  func    context var createCallback = function(func, context, argCount) { if (context === void 0) return func; //   -    switch (argCount == null ? 3 : argCount) { //      func case 1: return function(value) { //   ,    -,   func    return func.call(context, value); //     }; case 2: return function(value, other) { return func.call(context, value, other); }; case 3: return function(value, index, collection) { return func.call(context, value, index, collection); }; case 4: return function(accumulator, value, index, collection) { return func.call(context, accumulator, value, index, collection); }; } return function() { return func.apply(context, arguments); //    ,   func   , }; // c   ,      arguments }; //  ,  _.iteratee = function(value, context, argCount) { if (value == null) return _.identity; //     if (_.isFunction(value)) return createCallback(value, context, argCount); if (_.isObject(value)) return _.matches(value); //      return _.property(value); //      }; 

  
  
• attaching useful functions to the dash so that you can call a _.function like this (object to process, more arguments)
  
  code

  for collections

    _.each = _.forEach = function(obj, iteratee, context) { }; _.map = _.collect = function(obj, iteratee, context) { }; _.reduce = _.foldl = _.inject = function(obj, iteratee, memo, context) { }; _.reduceRight = _.foldr = function(obj, iteratee, memo, context) { }; _.find = _.detect = function(obj, predicate, context) { }; _.filter = _.select = function(obj, predicate, context) { }; _.reject = function(obj, predicate, context) { }; _.every = _.all = function(obj, predicate, context) { }; _.some = _.any = function(obj, predicate, context) { }; _.contains = _.include = function(obj, target) { }; _.invoke = function(obj, method) { }; _.pluck = function(obj, key) { }; _.where = function(obj, attrs) { }; _.findWhere = function(obj, attrs) { }; _.max = function(obj, iteratee, context) { }; _.min = function(obj, iteratee, context) { }; _.shuffle = function(obj) { }; _.sample = function(obj, n, guard) { }; _.sortBy = function(obj, iteratee, context) { }; //   ,          ,     _.groupBy = group(function(result, value, key) { }); _.indexBy = group(function(result, value, key) { }); _.countBy = group(function(result, value, key) { }); _.sortedIndex = function(array, obj, iteratee, context) { }; _.toArray = function(obj) { }; _.size = function(obj) { }; _.partition = function(obj, predicate, context) { }; 

  
  

  
  
  

  for arrays

    //  ,  ,   ,  _.first = _.head = _.take = function(array, n, guard) { }; _.initial = function(array, n, guard) { }; _.last = function(array, n, guard) { }; _.rest = _.tail = _.drop = function(array, n, guard) { }; _.compact = function(array) { }; _.flatten = function(array, shallow) { }; _.without = function(array) { }; _.uniq = _.unique = function(array, isSorted, iteratee, context) { }; _.union = function() { }; _.intersection = function(array) { }; _.difference = function(array) { }; _.zip = function(array) { }; _.object = function(list, values) { }; _.indexOf = function(array, item, isSorted) { }; _.lastIndexOf = function(array, item, from) { }; _.range = function(start, stop, step) { }; 

  
  

  
  
  

  for functions

    //      _.bind = function(func, context) { }; _.partial = function(func) { }; _.bindAll = function(obj) { }; _.memoize = function(func, hasher) { }; _.delay = function(func, wait) { }; _.defer = function(func) { }; _.throttle = function(func, wait, options) { }; _.debounce = function(func, wait, immediate) { }; _.wrap = function(func, wrapper) { }; _.negate = function(predicate) { }; _.compose = function() { }; _.after = function(times, func) { }; _.before = function(times, func) { }; _.once = _.partial(_.before, 2); //   before,       2 

  
  

  
  
  

  for objects

   _.keys = function(obj) { }; _.values = function(obj) { }; _.pairs = function(obj) { }; _.invert = function(obj) {}; _.functions = _.methods = function(obj) {}; _.extend = function(obj) { }; _.pick = function(obj, iteratee, context) { }; _.omit = function(obj, iteratee, context) { }; _.defaults = function(obj) { }; _.clone = function(obj) { }; _.tap = function(obj, interceptor) { }; _.isEqual = function(a, b) { }; _.isEmpty = function(obj) { }; _.isElement = function(obj) { }; _.isArray = nativeIsArray || function(obj) { }; //     -   _.isObject = function(obj) { }; _.each(['Arguments', 'Function', 'String', 'Number', 'Date', 'RegExp'], function(name) { }); //      if (!_.isArguments(arguments)) { _.isArguments = function(obj) { }; //  ,        } if (typeof /./ !== 'function') { _.isFunction = function(obj) { }; } _.isFinite = function(obj) {}; _.isNaN = function(obj) {}; _.isBoolean = function(obj) {}; _.isNull = function(obj) {}; _.isUndefined = function(obj) {}; _.has = function(obj, key) {}; 

  
  

  
  
  

  utilities

   _.identity = function(value) {}; _.constant = function(value) {}; _.noop = function(){}; _.property = function(key) { }; _.matches = function(attrs) { }; _.times = function(n, iteratee, context) { }; _.random = function(min, max) { }; _.now = Date.now || function() {}; _.escape = createEscaper(escapeMap); _.unescape = createEscaper(unescapeMap); _.result = function(object, property) { }; _.template = function(text, settings, oldSettings) { }; _.chain = function(obj) { }; 

  
  

  
  
• processing functions so that you can do so _ (object to process). function (more arguments)
  
  code

    //     : _(a).f1().f2().f3() var result = function(obj) { return this._chain ? _(obj).chain() : obj; }; //  ,  _.mixin = function(obj) { _.each(_.functions(obj), function(name) { var func = _[name] = obj[name]; _.prototype[name] = function() { //  c _   _() var args = [this._wrapped]; //    _,    "" push.apply(args, arguments); return result.call(this, func.apply(_, args)); // ,  ,     _(); }; }); }; // ,   _.mixin(_); // ,   , _.each(['pop', 'push', 'reverse', 'shift', 'sort', 'splice', 'unshift'], function(name) { var method = ArrayProto[name]; _.prototype[name] = function() { var obj = this._wrapped; method.apply(obj, arguments); //  this-       . if ((name === 'shift' || name === 'splice') && obj.length === 0) delete obj[0]; // .  ,    return result.call(this, obj); }; }); //   _.each(['concat', 'join', 'slice'], function(name) { var method = ArrayProto[name]; //       _.prototype[name] = function() { return result.call(this, method.apply(this._wrapped, arguments)); }; }); //     x    _().f1().f2().f3() _.prototype.value = function() { return this._wrapped; }; 

  
  

Cutting out js organs

• variable processing
  
  code

   var root = this //   ,   this   var i, length = obj.length; //   ,        for (i = 0, length = keys.length; i < length; i++) { iteratee(obj[keys[i]], keys[i], obj); } for (; i < length; i++) if (array[i] === item) return i; // i    slice.call(array, Math.max(array.length - n, 0)); //     args.concat(slice.call(arguments)) //      for (var key in obj) if (_.has(obj, key)) keys.push(key); //     obj[prop] = source[prop]; //      

  
  
• function processing
  
  code

    (function() { }.call(this)); //  , this    if (!(this instanceof _)) return new _(obj); //  ,   -  var createCallback = function(func, context, argCount) { return function(value) { //    ,      return func.call(context, value); }; }; _.each = _.forEach = function(obj, iteratee, context) {}; //       _ _.find = _.detect = function(obj, predicate, context) { predicate = _.iteratee(predicate, context); //   predicate      _.some(); //  ,    ,   }; _.some(obj, function(value, index, list) { }); //          //  , var group = function(behavior) { //       return function(obj, iteratee, context) { //  ,     behavior(result, value, key); //    -   return result; }; }; _.indexBy = group(function(result, value, key) { //   result[key] = value; }); //  ,    , ,  ,   ,    ,      var flatten = function(input, shallow, strict, output) { for (var i = 0, length = input.length; i < length; i++) { flatten(value, shallow, strict, output); //      } }; //      _.flatten = function(array, shallow) { return flatten(array, shallow, false, []); }; //  var x = func.bind(obj), ,   ,   : x(), //   -  obj.func(),   this  func  obj nativeBind.apply(func, slice.call(arguments, 1)) //      ,        //             this   obj[key] = _.bind(obj[key], obj); //     _.memoize = function(func, hasher) { var memoize = function(key) {}; memoize.cache = {}; //     return memoize; }; //    setTimeout(function(){ return func.apply(null, args); }, wait); // ,       _.property = function(key) { return function(obj) { return obj[key]; //         }; }; //   _.prototype[name] = function() { //   name    var args = [this._wrapped]; push.apply(args, arguments); return result.call(this, func.apply(_, args)); }; //      : var x = new _; x[name](); 

  
  
• checks
  
  code

   typeof exports !== 'undefined' //  if (length === +length) //    var keys = obj.length !== +obj.length && _.keys(obj), //   ,   _.keys length = (keys || obj).length, //    ,  ,    results = Array(length), currentKey; memo = obj[keys ? keys[index++] : index++]; //   ,  ,   if (!index) throw new TypeError(reduceError); //   -    if (array == null) return void 0; //       if (n == null || guard) return array[0]; if (n < 0) return []; return slice.call(array, 0, n); if (!(this instanceof bound)) //   this   new bound _.isBoolean = function(obj) { //     return obj === true || obj === false || toString.call(obj) === '[object Boolean]'; }; //        ,    func if (nativeBind && func.bind === nativeBind) return nativeBind.apply(func, slice.call(arguments, 1)); hasOwnProperty.call(source, prop) //     ( ) if (key in obj) result[key] = obj[key]; //      if (obj[prop] === void 0) obj[prop] = source[prop]; //    //       try { var render = new Function(settings.variable || 'obj', '_', source); } catch (e) { //   e.source = source; throw e; //      } 

  
  
• beautiful moments
  
  code

   while (index--) { //       currentKey = keys ? keys[index] : index; memo = iteratee(memo, obj[currentKey], currentKey, obj); } //     - value, this - value,    args //  func.apply(x, [1, 2, 3, 4])   x.func(1, 2, 3, 4),  func.call(x, [1, 2, 3, 4]) -  x.func([1, 2, 3, 4]) (isFunc ? method : value[method]).apply(value, args) var mid = low + high >>> 1; //    2 //     _  ,        _.each(['Arguments', 'Function', 'String', 'Number', 'Date', 'RegExp'], function(name) { _['is' + name] = function(obj) { return toString.call(obj) === '[object ' + name + ']'; }; }); 

  
  
• argument sets
  
  code

   //  - (iteratee)     obj, this-   -  context // obj -    function(obj, iteratee, context) {}; // , -        -  , //  -  , value -   , index -     function(accumulator, value, index, collection) {}; memo = iteratee(memo, obj[currentKey], currentKey, obj); // predicate      ,  true,    function(obj, predicate, context) {}; // , /  , /; function(value, index, list) { } // method   ,   -,       function(obj, method) {}; // key - ,     ,         . function(obj, key) {}; // attrs -  key,            function(obj, attrs) { }; // guard  ,      function(obj, n, guard) {}; //         function(array, n, guard) {}; //     ,     function(func){}; //      -     function(obj){}; 

  
  

Saw the rest, learn to use Firebug and documentation , and then collect everything back Vasya remains as a homework assignment.


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