详解JavaScript函数callee、call、apply的区别

function sum(num){
 if(num <= 1){
 return 1;
 }else{
 console.log(num, arguments.callee(num-1));
 return num  arguments.callee(num-1);
 }
}

console.log(sum(3));

function box(num1,num2){
 return num1+num2;
}

function sum(num1,num2){
 //this 表示全局作用域，浏览器环境下window，node环境global，[]表示传递的参数
 return box.apply(this,[num1,num2]);

 //或者狼蚁网站SEO优化写法arguments可以当数组传递
 //return box.apply(this,arguments);
}

console.log(sum(10,10)); //输出结果: 20

function box(num1,num2){
 return num1+num2;
}

function sum2(num1,num2){
 return box.call(this,num1,num2);
}

console.log(sum(10,10)); //输出结果: 20