javascript高级程序设计70 71
加参数和不加参数
//变量：基本类型、引用类型,参数传递 高级程序设计69页
var color = "red";
function changeColor(color){ //参数color实际就是changeColor函数的局部变量。所有函数的参数都是按值传递
console.log(arguments) //[callee:function,Symbol()]
if(color === "red"){
color = "blue";
}else{
color = "blue";
}
}
changeColor(color);
console.log(color) //red
var color = "red";
function changeColor(){
console.log(arguments) //[callee:function,Symbol()]
if(color === "red"){
color = "blue";
}else{
color = "blue";
}
}
changeColor();
console.log(color) //blue
//全局变量和局部变量
var a = 10;
sayHi();
function sayHi()
{
var a = a + 10;
alert(a);
return a; //return的a不会覆盖全局变量a,所以下面的alert(a) //10
}
alert(a);
alert(sayHi()+10);
执行结果：NaN 10 NaN NaN
var a = 10;
sayHi();
function sayHi()
{
var a = "a" + 10;
alert(a);
alert(typeof a);
return a; //return的a不会覆盖全局变量a,所以下面的alert(a) //10
}
alert(a);
alert(sayHi()+10);
执行结果：a10 string 10 a10 string a1010
