1、 (function() {})()
2、(function(){}())
Benefits of immediate function execution: Creates an isolated scope. Avoids naming conflict issues.
important point:
- Immediate execution function: a function that can be executed immediately without calling
You can also pass parameters in, the second parentheses can be seen as calling a function
You can give the immediate execution function a name
When there are multiple immediate execution functions, a semicolon should be added at the end of the immediate execution functions.
example:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
</head>
<body>
<script>
// 1.立即执行函数: 不需要调用，立马能够自己执行的函数
function fn() {
console.log(1);
}
fn();
// 2. 写法 也可以传递参数进来
// 1.(function() {})() 或者 2. (function(){}());
(function(a, b) {
console.log(a + b);
var num = 10;
})(1, 2); // 第二个小括号可以看做是调用函数
(function sum(a, b) {
console.log(a + b);
var num = 10; // 局部变量
}(2, 3));
// 3. 立即执行函数最大的作用就是 独立创建了一个作用域, 里面所有的变量都是局部变量 不会有命名冲突的情况
</script>
</body>
</html>Reference: Dark Horse Programmer