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What is the purpose of a self executing function in javascript?
What meens in JS write a code like this:
(function (window) { })(window); or this:
(function () { })(); 
- It's a duplicate so I voted to close, though I think the answers there aren't as good as the answers here. specially not this wrong +17 answergdoron– gdoron2012-07-03 21:14:11 +00:00Commented Jul 3, 2012 at 21:14
- If someone looks for PHP 7, where this has been introduced. stackoverflow.com/questions/3568410/…Franz Holzinger– Franz Holzinger2019-11-15 15:12:42 +00:00Commented Nov 15, 2019 at 15:12
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3 Answers
It creates a closure, a private scope hiding the variables from the global object
// Somewhere... var x = 2; ... ... // Your code var x = "foo" // you override the x defined before. alert(x); // "foo" But when you use a closure:
var x = 2; // Doesn't change the global x (function (){ var x = "foo";})(); alert(x); // 2 Regarding to the syntax, it's just a self executed function, you declare it and then execute it.
4 Comments
Rodrigo Reis
TY! And when I pass a variable? Like this:
(function (window) { })(window);
gdoron
@RigoReis. They become variables in the function. it's used for minifing code, nothing "real"
Rodrigo Reis
TY'll folks help me so much, special thanks to @gdoron
gdoron
@RigoReis. No problem. Good luck in your new js way.
It's a self invoking anonymous function or a function expression. It prevents you from creating variables in the global scope. It also calls the function right away.
function someFunc() { // creates a global variable } var someFunc = function () { // creates a global variable } (function(){ // creates an anonymous function and // runs it without assigning it to a global variable })(); answered Jul 3, 2012 at 20:57
Ufuk Hacıoğulları
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It's called a closure. It helps control the scope of variables since Javascript hoists variables to the top of their scope. They're also anonymous functions which execute or initialize immediately.
