通過閉包訪問到了局部變量text
function greeting(name) {
var text = 'Hello ' + name; // local variable
// 每次調(diào)用時凿叠，產(chǎn)生閉包龟虎，并返回內(nèi)部函數(shù)對象給調(diào)用者
return function () {
console.log(text);
return text
}
}
var sayHello = greeting("Closure");
sayHello() // 通過閉包訪問到了局部變量text
let和閉包解決this丟失
for (let i = 0; i <= 5; i++) {//let是關(guān)鍵
(function () {//包一層自執(zhí)行行數(shù)瘟檩，帶參數(shù)
setTimeout(function (timer) {
console.log(i)
}, i * 1000)
})(i)
}
使用閉包對外暴露方法
(function () {
const a = 10;
const b = 20;
function add(num1, num2) {
num1 = !!num1 ? num1 : a;
num2 = !!num2 ? num2 : b;
return num1 + num2;
}
this.add = add;//方法add被作為一個閉包糖权，對外暴露了一個公共方法
})();
console.log(add(10, 20));
高級閉包demo
function newClosure(someNum, someRef) {
// Local variables that end up within closure
let num = someNum;
let anArray = [1, 2, 3];
let ref = someRef;
return function (x) {
num += x;
anArray.push(num);
console.log('num: ' + num +
'\nanArray ' + anArray.toString() +
'\nref.someVar ' + ref.someVar);
}
}
closure1 = newClosure(40, {someVar: 'closure 1'});
closure1(5);//等同于return
closure1(5);//上次執(zhí)行的結(jié)果還保存著哦
