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1.概念
函數(shù)就是重復(fù)執(zhí)行的代碼片
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>函數(shù)</title>
<script type="text/javascript">
function fnChange(){
alert("hello world!"); /*設(shè)置函數(shù)*/
}
function fnStyle(){
var oDiv = document.getElementById("div1");
oDiv.style.color = 'red';
oDiv.style.fontSize = '70px';
}
</script>
</head>
<body>
<div id="div1" onclick="fnChange()">123456</div> <!--點擊時調(diào)用函數(shù)-->
<input type="button" name="" value="點擊" onclick = "fnStyle()">
</body>
</html>
2.提取行間事件
window.onload = function(){
var oBut = document.getElementById('btn01');
oBut.onclick = fnStyle; /將事件的屬性和一個函數(shù)關(guān)聯(lián),函數(shù)不寫小括號,寫了會馬上執(zhí)行/
function fnStyle(){
var oDiv = document.getElementById("div1");
oDiv.style.color = 'red';
oDiv.style.fontSize = '70px';
}
}
</script>
</head>
<body>
<div id="div1" onclick="fnChange()">123456</div> <!--點擊時調(diào)用函數(shù)-->
<input type="button" name="" value="點擊" id="btn01">
</body>
3.匿名函數(shù)
oBut.onclick = function(){
var oDiv = document.getElementById("div1");
oDiv.style.color = 'red';
oDiv.style.fontSize = '70px';
}; /匿名函數(shù),直接賦予/
**4.網(wǎng)頁換膚**
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<link rel="stylesheet" type="text/css" href="../CSS/btn02.css" id="link01">
<script type="text/javascript">
window.onload = function(){
var oBtn01 = document.getElementById('btn01');
var oBtn02 = document.getElementById('btn02');
var oLink01 = document.getElementById('link01');
oBtn01.onclick = function(){
oLink01.href = "../CSS/btn02.css";
}
oBtn02.onclick = function(){
oLink01.href = "../CSS/btn01.css";
}
}
</script>
<title>網(wǎng)頁變換</title>
</head>
<body>
<input type="button" name="" value="皮膚一" id="btn01">
<input type="button" name="" value="皮膚二" id="btn02">
</body>
</html>
5.變量與函數(shù)預(yù)解析
JavaScript解析過程分為兩個階段,先是編譯階段,然后執(zhí)行階段,在編譯階段會將function定義的函數(shù)提前,并將var定義的變量聲明提前,將它賦值為undefined,即定義前調(diào)用
6.函數(shù)傳參
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>形參</title>
<script type="text/javascript">
window.onload = function(){
function fnChangestyle(myStyle,val){ /*形參*/
var oDiv = document.getElementById('div1');
oDiv.style[myStyle] = val;
}
fnChangestyle('color','red') /*實參*/
}
</script>
</head>
<body>
<div id="div1">123456</div>
</body>
</html>
函數(shù)‘return’關(guān)鍵字
(1)返回函數(shù)執(zhí)行的結(jié)果
(2)結(jié)束函數(shù)的運行
(3)阻止默認行為
function fnAdd(a,b){
var c = a + b;
return c; /返回c值,結(jié)束函數(shù)/
}
var iNum = fnAdd(5,8);
alert(iNum);
7.加法運算
var oInput01 = document.getElementById('input01');
var oInput02 = document.getElementById('input02');
var oBtn = document.getElementById('btn');
oBtn.onclick = function(){
var iVal01 = parseInt(oInput01.value); /*轉(zhuǎn)化為實數(shù)*/
var iVal02 = parseInt(oInput02.value);
alert(iVal01+iVal02);
}
8.條件語句
通過條件來控制程序的走向,就需要用到條件語句。
運算符
(1)算術(shù)運算符:+、 -、 、 /、 %(求余)
(2)賦值運算符:=、+=、-=、=、/=、%=、++等同于加一
(3)條件運算符:==、===、>、>=、<、 <=、 != &&(而且,和)、||(或者,與)、?。ǚ瘢?/p>
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>條件運算符</title>
<script type="text/javascript">
var iVal01 = 2; /*實數(shù)型*/
var iVal02 = '2'; /*字符型*/
/*彈出相等,==,是不考慮類型*/
/*if(iVal01==iVal02){
alert('相等')
}
else{
alert('不相等')
}*/
/*===,考慮類型*/
if(iVal01===iVal02){
alert('相等')
}
else{
alert('不相等')
}
/*!5<2將運行結(jié)果取反*/
if(!5<2){
alert('小于');
}
else{
alert('不小于');
}
</script>
</head>
<body>
</body>
</html>
9.多重循環(huán)
(1)if語句
if(.....){
....
}
else if(....){
.....
}
else{
......
}
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>切換</title>
<style type="text/css">
div{
width: 100px;
height: 300px;
background-color: aqua;
}
</style>
<script type="text/javascript">
window.onload = function(){ /*整個頁面加載完成后,在加載*/
var oIpt = document.getElementById('ipt');
var oDiv = document.getElementById('div1');
oIpt.onclick = function(){
if(oDiv.style.display=="block" || oDiv.style.display==""){
/*用if語句切換,第一步,oDiv.style.disply讀取屬性值,如果沒有寫等于null,執(zhí)行else*/
oDiv.style.display = 'none';
}
else{
oDiv.style.display = 'block';
}
}
}
</script>
</head>
<body>
<input type="button" name="" value="切換" id="ipt">
<div id="div1"></div>
</body>
</html>
(2)switch語句
多重if else 語句可以換成性能更高的switch
switch (....){
case 1:
.................;
break;
case 2:
.................;
break;
case 3:
.................;
break;
case 4:
.................;
break;
default:
..................;
}
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