3-02函数

知识点：

函数返回值

返回值和输出值的差别

//输出是直接输出到浏览器上的
//返回备用，可以复制给等号前面的变量

同一个环境下不允许出现两个一样的函数名；

函数的参数不允许有默认值；

所有的JS都是是区分大小写的，

arguments参数

示例：

<script type="text/javascript">
function Add(){
document.writeln(66);//输出

return 88；//返回
}
var b = Add();
alert(b);=  66 输出值 undefined返回值   88返回值

var box = document.getElementById("box");
document.writeln(box.innerHTML+"555")

 

function Add(){
document.writeln(arguments[1]);
}
Add(3,5);

</script>

<script type="text/javascript">
function Add(){
for (var p in arguments){
document.writeln(p);

document.writeln(arguments[p]);
}
}
Add(3,5,7,9);=0,1,2,3     3,5,7,9

</script>

<script type="text/javascript">
function Add(){
for (var p in arguments){
if (arguments[p]==3 || arguments[p]==7)
document.writeln(arguments[p]);
}
}
Add(3,5,7,9);=3,7

</script>

<script type="text/javascript">
var box = document.getElementById("box");
var a = function(){
box.style.background="red";
}
var b = function(){
box.style.background="#fff";
}
box.onmouseover = a;
box.onmouseout = b;

 

<script type="text/javascript">
var box = document.getElementById("box");
var a = function(e){
box.style.background= e.type == "mouseover"?"red":"white";三目运算
}

box.onmouseover = a;
box.onmouseout = a;
</script>

<style type="text/css">
div{
border:10px darkseagreen solid;
}
</style>
<div id="box">66</div>

<script type="text/javascript">
//事件与事件对象
var box = document.getElementById("box");
var i = 0;mcolor = null;
var a = function(){
i++;
if(i==1) mcolor = "red";
else if(i==2) mcolor = "blue";
else if(i==3) mcolor = "green";
else mcolor = "pink";
box.style.background = mcolor;
}

box.onclick = a;

</script>

</script>