Javascript Interview Questions

Not so long ago, I was puzzled by the search for a job, in connection with which I visited the n-th number of interviews and heard many interesting questions. There are a lot of articles on the network with questions on JS, so I will try to select questions that I have not yet seen. There are no questions of type What is a closure? , Inheritance in JavaScript or Make ajax request on VanillaJS . By the way, I advise you to look for answers to these questions before reading the article :) Under the cut questions like “with a trick”. It is unlikely that any of them will fall for you, but I hope the article will set you on a “dirty trick” thinking, and remind you of some slippery places and javascript underwater pebbles.

Hoisting

Hoisting is the ascent of variables declared in a function. Here you can learn in detail about how it happens.
But an interesting question:

(function() {
	f();

	f = function() {
		console.log(1);
	}
})()

function f() {
	console.log(2)
}

f();

?



— . :

(function() {
	var x = 1;

	function x() {};
	
	console.log(x);	
})()

?



. : JSLint.
var function expression

javascript :

var obj = {
	a: 1
};

(function(obj) {
	obj = {
		a: 2
	};

})(obj);

console.log(obj.a);

, . , .

— , . . . .

Logger = function(logFn) {
	
	_logFn = logFn;

	this.log = function(message) {
		_logFn(new Date() + ": " + message);
	}
}

var logger = new Logger(console.log);

logger.log("Hi!");
logger.log("Wazzup?");

? ?



UPD: 5