通过闭包访问到了局部变量text
function greeting(name) {
var text = 'Hello ' + name; // local variable
// 每次调用时，产生闭包，并返回内部函数对象给调用者
return function () {
console.log(text);
return text
}
}
var sayHello = greeting("Closure");
sayHello() // 通过闭包访问到了局部变量text
let和闭包解决this丢失
for (let i = 0; i <= 5; i++) {//let是关键
(function () {//包一层自执行行数，带参数
setTimeout(function (timer) {
console.log(i)
}, i * 1000)
})(i)
}
使用闭包对外暴露方法
(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被作为一个闭包，对外暴露了一个公共方法
})();
console.log(add(10, 20));
高级闭包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);//上次执行的结果还保存着哦
