JavaScriptの基礎知識まとめ(10) クロージャと即時実行関数

//例子function a() {    function b(){        var bbb = 234;        console.log(aaa)
    }    var aaa = 123;    return b;
}var glob = 100;var demo = a();
demo();

function a (){    var num  = 100;    function b(){
        num ++;        console.log(num);
    }    return b;
}var demo = a();
demo();//打印101demo();//打印102

function test(){    var num = 100;    function a(){
        num ++;        console.log(num);
    };    function b(){
        num --;        console.log(num);
    };    return [a,b]
}var myArr = test();
myArr[0]();//打印101myArr[1]();//打印100
function eater(){    var food = "";    var obj ={        eat : function(){            console.log("i am eating" + food)
        },        push : function (myFood){
            food = myFood;
        }
    }    return obj;
}var eater1 = eater();
eater1.push('banana');
eater1.eat();//打印出 i am eating banana

function a(){
    
}function b(){
    
}

(function (aaa,bbb,ccc){    var a = 234;    var b = 123;    var c = a+b;    console.log(c)    return c}(1,2,3))
执行完立即被销毁
// 怎么去接收他var num = (function (aaa,bbb,ccc){    var a = 234;    var b = 123;    var c = a+b;    console.log(c)    return c}(1,2,3))
立即执行函数有两种写法
//第一种(function(){}());//w3c 建议第一种//第二种(function(){})();
扩展
只有表达式才可以被执行符号执行
var test = function (){}()//也可以被执行+ function test(){}()//也可以被执行 以此类推- !号也可以function test(){    console.log(a+b+c+d)}(1,2,3,4)//不执行也不报错