JavaScript学习笔记（四）

function sum(num1,num2){
    return num1 + num2;
}
alert(sum(10,20)); //30
var anotherSum = sum; //相当于把another指向sum所指向的空间
alert(anotherSum(10,10)); //20
sum = null;
alert(anotherSum(10,15)); //25

alert(sum(10,20)); //30
function sum(num1,num2){
    return num1+num2;
}

alert(sum(10,20));//TypeError: sum is not a function
var sum =function(num1,num2){
    return num1+num2;
}
//在执行到函数所在的语句之前，变量sum中不会保存有对函数的引用