Introduction to the differences in how JS functions are defined_Basic knowledge

There are two ways to define functions in JS:

(1) Typical function declaration

function slide(arguments){ 
//...code
}

(2) Define functions in the form of function expressions

var slide = function(arguments){
//...code
}

Although the above two methods are logically equivalent, there are still some small differences:

Difference 1: The function in Example 1 will be loaded into the scope before the code is executed, while in Example 2 it will not be defined until the code is executed to that line;
Difference 2: The function declaration assigns a name to the function, while the function expression creates an anonymous function and then assigns the anonymous function to a variable;

Look at the example below:

function factorial(num){
if(num<=1){
return 1;
}
else {
return num*arguments.callee(num-1);
}
}
var anotherFactorial = factorial;
factorial = null;
console.log(anotherFactorial);//输出factorial(){}，有函数名
若是以函数表达式定义
var factorial = function(num){
//...code
}
//...code
console.log(anotherFactorial);//输出function(){}，匿名函数

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