A brief discussion on the differences in JS function definition methods

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 The methods are logically equivalent, but 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 be loaded into the scope when the code is executed to that line. There will be a definition;

Difference 2: The function declaration will assign 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 following example:

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

If it is defined by a function expression

var factorial = function(num){
//...code
}
//...code
console.log(anotherFactorial);//输出function(){}，匿名函数