javascript IIFE in depth

javascript IIFE in depth

function type

1. 函数表达式

x = function (){
    console.log(x); 
}
ƒ (){
    console.log(x); 
}

x;
ƒ (){
    console.log(x); 
}

x();
ƒ (){
    console.log(x); 
}

window.x;
ƒ (){
    console.log(x); 
}

x = function x(){
    console.log(x); 
}
ƒ x(){
    console.log(x); 
}

x();
ƒ x(){
    console.log(x); 
}

window.x;
ƒ x(){
    console.log(x); 
}

2. 函数声明

function x(){
    console.log(x); 
}

x();
ƒ x(){
    console.log(x); 
}

window.x
ƒ x(){
    console.log(x); 
}

考察知识点

1. closure
2. IIFE
3. hoisting
4. scope
5. function declaration / function expression
6. named function / anonymous function

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions

closure

https://javascript.info/closure

js var hoisting

1. function

2. var

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demo

https://muyiy.cn/question/js/33.html

// 下面的代码打印什么内容，为什么？

var b = 10;
(function b(){
    b = 20;
    console.log(b); 
})();

var b = 10;
(function b(){
    b = 20;
    console.log(b); 
    console.log(window.b); 
})();


ƒ b(){
    b = 20;
    console.log(b); 
    console.log(window.b); 
}
// 10

函数表达式的函数名是常量，无法二次赋值(在正常模式下静默失效，在严格模式下报错)

非匿名自执行函数，函数名只读

'use strict';

var b = 10;
(function b(){
    'use strict';
    b = 20;
    console.log(b); 
    console.log(window.b); 
})();

//  Uncaught TypeError: Assignment to constant variable.
    at b (<anonymous>:4:7)
    at <anonymous>:7:3

https://github.com/Advanced-Frontend/Daily-Interview-Question/issues/48#issuecomment-615547271

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scope & hoisting

https://www.adequatelygood.com/JavaScript-Scoping-and-Hoisting.html

https://repl.it/@xgqfrms/Function-hoisting-greater-var-hoisting

https://stackoverflow.com/questions/7506844/javascript-function-scoping-and-hoisting

https://www.sitepoint.com/5-typical-javascript-interview-exercises/

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