Javascript immediately invoked function patterns

Question

What do you call these patterns? What is the difference between them? When would you use each? Are there any other similar patterns? ``` (function() { console.log(this); // window })(); (function x() { console.log(this); // window })(); var y = (function() { console.log(this); // window })(); var z = function() { console.log(this); // window }(); ``` EDIT: I just found two more seemingly redundant ways to do this by naming the functions in the last two cases... ``` var a = (function foo() { console.log(this); // window })(); var b = function bar() { console.log(this); }(); ``` EDIT2: Here is another pattern provided below by @GraceShao which makes the function accessible outside the function scope. ``` (x = function () { console.log(this); // window console.log(x); // function x() {} })(); console.log(x); // function x() {} // I played with this as well // by naming the inside function // and got the following: (foo = function bar() { console.log(this); // window console.log(foo); //…

Accepted Answer

Here are your functions again with some comments describing when/why they might be useful:

```
(function() {
    // Create a new scope to avoid exposing 
    // variables that don't need to be
    // This function is executed once immediately
})();

(function fact(i) {
    // This named immediately invoked function 
    // is a nice way to start off recursion
    return i <= 1 ? 1 : i*fact(i - 1);
})(10);

var y = (function() {
    // Same as the first one, but the return value 
    // of this function is assigned to y
    return "y's value";
})();

var z = function() {
    /* This is the exact same thing as above 
     (except it is assigned to z instead of y, of course).
     The parenthesis in the above example don't do anything
     since this is already an expression
    */
}();
```

Javascript immediately invoked function patterns

Solution

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