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);   // function bar() {}
    console.log(bar);   // function bar() {}
})();
console.log(foo);       // function bar() {}
console.log(bar);       // undefined
javascript function design-patterns
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