iife

I came through this fun quiz on the internet. console.log((function(x, f = (() => x)){ var x; var y = x; x = 2; return [x, y, f()] })(1)) and the choices were: [2,1,1] [2, undefined, 1] [2, 1, 2] [2, undefined, 2] I picked solution 2 TBH, basing that on that x has been redefined, y was declared and defined with no value, and that f has a different scope hence getting the global x memory spot than function x memory spot. However, I tried it in jsbin.com and I found it was solution 1, while I was not sure why that happened I messed with the function body and I removed var x from the function

I'm trying to immediately invoke a function without using IIFE pattern (enclosing a function definition inside parentheses). Here I see two scenarios: When a function declaration is invoked immediately: gives SyntaxError . When a function expression is invoked immediately: executes successfully . Example 1: gives SyntaxError //gives `SyntaxError` function() { console.log('Inside the function'); }(); Example 2: Executes without any error // Executes without any error var x = function() {console.log('Inside the function')}(); // Inside the function So, I have these doubts: With this approach,

I have always seen code like this: (function(){ //code here })(); How does this code work? Which function receives which parameters? (function(factory){ //code here }(function($){ //other code here })); function($){ //other code here } This block is passed as a parameter to the outer IIFE. It might be clearer to write it like this: var factoryDef = function($) { ... }; (function(factory) { // this is the outer IIFE var someVar = {}; // you can call: factory(someVar); // the previous line calls factoryDef with param someVar }(factoryDef)); So factory(someVar) is the same as factoryDef({}) ; the

This question already has an answer here: Are “(function ( ) { } ) ( )” and “(function ( ) { } ( ) )” functionally equal in JavaScript? [duplicate] 3 answers Sometimes I see this: (function() { alert("hi"); })(); And sometimes I see this: (function() { alert("hi"); }()); Note the placement of the closing paren for the function object. What is the difference? I can't figure it out. Is either preferable for any reason? Edit: Also, this does not work: function() { alert("hi"); }(); Which seems weird, since it is valid if wrapped in parentheses, as in example 2. I don't understand why wrapping it

This question already has an answer here: What does “var FOO = FOO || {}” (assign a variable or an empty object to that variable) mean in Javascript? 7 answers First, a pseudo code example: ;(function(foo){ foo.init = function(baz) { ... } foo.other = function() { ... } return foo; }(window.FOO = window.FOO || {})); Called like so: FOO.init(); My question: What is the technical name/description of: window.FOO = window.FOO || {} ? I understand what the code does... See below for my reason(s) for asking. Reason for asking: I'm calling the passed in global like so: ;(function(foo){ ... foo vs.

Is there any difference between (function (){alert('')} ()) vs (function (){alert('')}) () Both works but when should I use each ? The wrapping parentheses are only there to force the parser to parse the construct as a function expression, rather than a function declaration. This is necessary because it's illegal to invoke a function declaration, but legal to invoke a function expression. To that end, it doesn't matter where the invoking parentheses go. It also doesn't matter how you force the function to be parsed as an expression. The following would work just as well: !function () { alert('

The following TypeScript: enum PrimaryColors { Red, Green, Blue }; Produces the following JavaScript: var PrimaryColors; (function (PrimaryColors) { PrimaryColors[PrimaryColors["Red"] = 0] = "Red"; PrimaryColors[PrimaryColors["Green"] = 1] = "Green"; PrimaryColors[PrimaryColors["Blue"] = 2] = "Blue"; })(PrimaryColors || (PrimaryColors = {})); ; I am embarrassed to admit that I don't understand what the JavaScript is doing. The function in parentheses is assigning string values using another assignment as the index/key. I have not seen anything like this before. And what is the purpose of the