JavaScript ?? ??
JavaScript ???? 4?? ?? ??? ????.
? ??? ???? ???? ????.
? ???
????? Javascript?? ??? ??? ? ?? ??? ?????.
Note: ??????? ??? ?????? ? ?? ??? ? ????. ?
JavaScript ?? ??
?? ??? ??? ??? ??? ??? ?????.
?? ??? ??? ??? ??? ?? ?????.
??? ????
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>php中文網(wǎng)(php.cn)</title>
</head>
<body>
<p>
全局函數(shù) (myFunction) 返回參數(shù)參數(shù)相乘的結(jié)果：
</p>
<p id="demo"></p>
<script>
function myFunction(a, b) {
return a * b;
}
document.getElementById("demo").innerHTML = myFunction(10, 2);
</script>
</body>
</html>????? ???? ??? ???
? ??? ?? ???? ??? ????. ??? JavaScript??? ?? ?? ?? ?????.
HTML? ?? ?? ??? HTML ??? ????? ?? ??? HTML ???? ????.
????? ??? ??? ???? ?(? ??)???. ?? ??? ???? ? ??? ??? ???.
myFunction() ? window.myFunction()? ?????.
Instance
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>php中文網(wǎng)(php.cn)</title>
</head>
<body>
<p>全局函數(shù) myFunction() 會(huì)自動(dòng)成為 window 對(duì)象的方法。</p>
<p>myFunction() 類似于 window.myFunction()。</p>
<p id="demo"></p>
<script>
function myFunction(a, b) {
return a * b;
}
document.getElementById("demo").innerHTML = window.myFunction(10, 2);
</script>
</body>
</html>????? ???? ??? ???
?: ?? JavaScript ??? ???? ???? ????? ?? ????? ??, ?? ??, ??? ?? ??? ?? ?? ?? ??? ?? ??? ? ????.
?? ??
??? ?? ??? ?? ???? ??? this? ?? ?? ??? ???.
? ?????? ?? ??? ???? ?(? ??)???.
? ?????? ??? this ?? ? ?????.
Instance
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>php中文網(wǎng)(php.cn)</title>
</head>
<body>
<p>在 HTML 中 <b>this</b> 的值, 在全局函數(shù)是一個(gè) window 對(duì)象。</p>
<p id="demo"></p>
<script>
function myFunction() {
return this;
}
document.getElementById("demo").innerHTML = myFunction();
</script>
</body>
</html>????? ???? ??? ???
??: ??? ?? ??? ???? ??? ?? ??? ???. ? ??? ??? ???? ????? ?? ??? ? ????.
?????? ?? ??
JavaScript??? ??? ??? ???? ??? ? ????.
?? ???? ? ?? ??(firstName ? lastName)? ???(fullName)? ?? ??(myObject)? ????.
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>php中文網(wǎng)(php.cn)</title>
</head>
<body>
<p>myObject.fullName() 返回 John Doe:</p>
<p id="demo"></p>
<script>
var myObject = {
firstName:"John",
lastName: "Doe",
fullName: function() {
return this.firstName + " " + this.lastName;
}
}
document.getElementById("demo").innerHTML = myObject.fullName();
</script>
</body>
</html>????? ???? ??? ???
fullName ???? ?????. ??? ??? ????. myObject? ??? ??????.
? ???? JavaScript ??? ???? ????. ?????? ? ?? myObject ?????.
???? ???????! fullName ???? ???? ? ?? ?????.
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>php中文網(wǎng)(php.cn)</title>
</head>
<body>
<p>在一個(gè)對(duì)象方法中 ，<b>this</b> 的值是對(duì)象本身。</p>
<p id="demo"></p>
<script>
var myObject = {
firstName:"John",
lastName: "Doe",
fullName: function() {
return this;
}
}
document.getElementById("demo").innerHTML = myObject.fullName();
</script>
</body>
</html>????? ???? ??? ???
Tips: ??? ?? ???? ???? this? ?? ?? ??? ???.
???? ???? ?? ??
?? ?? ?? new ???? ???? ???? ?????.
? ??? ??? ??? ???? ???? JavaScript ??? ??? ?? ??? ????.
Instance
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>php中文網(wǎng)(php.cn)</title>
</head>
<body>
<p>該實(shí)例中， myFunction 是函數(shù)構(gòu)造函數(shù):</p>
<p id="demo"></p>
<script>
function myFunction(arg1, arg2) {
this.firstName = arg1;
this.lastName = arg2;
}
var x = new myFunction("John","Doe")
document.getElementById("demo").innerHTML = x.firstName;
</script>
</body>
</html>????? ???? ??? ???
???? ???? ? ??? ?????. ? ??? ???? ??? ???? ?????.
Tips: ???? this ????? ?? ????. this? ?? ??? ??? ? ??(? ??)? ?????? ? ?????. ?
?? ???? ?? ????
JavaScript?? ??? ?????. JavaScript ???? ??? ???? ????.
call() ? apply()? ?? ??? ?? ??????. ? ?? ???? ???? ??? ??? ? ???, ? ??? ??? ? ?? ?? ??? ?? ???? ???.
function myFunction(a, b) {
return a * b;
}
myFunction.call(myObject, 10, 2); // Return 20
function myFunction(a, b) {
return a * b;
}
myArray = [10,2];
myFunction.apply(myObject, myArray); // 20? ?????
? ?? ?? ?? ??? ? ?? ????? ?????. ? ??? ???? ? ?? ????? ????. Apply? ???? ??? ?????. ?, ?? ????? ??? ??? ???? ???? ??, call? ??? ????? ?????(? ?? ?????? ??).
JavaScript ?? ????? ????? ??? ????? ??? ??? ? ? ?? ????? this? ?? ???.
JavaScript ??? ????? ? ?? ????? ?? null??? ???? ?? ?? ?? ??? ?? ?????.
Tips: call() ?? apply() ???? ?? ? ?? ???? ?? ??? ? ???? ??? ? ????.
