JavaScript学习与实践（8）
函数是一个可以重用的代码快，当一个事件出发或者函数本上被调用的时候。
怎么来调用一个函数呢？
<html>
<head>
<script type="text/javascript">
function myfunction()
{
alert("HELLO")
}
</script>
</head>
<body>
<form>
<input type="button"
onclick="myfunction()"
value="Call function">
</form>
<p>By pressing the button, a function will be called. The function will alert a message.</p>
</body>
</html>
给一个函数传参数，并在函数中应用他，在下面有两个例子，
<html>
<head>
<script type="text/javascript">
function myfunction(txt)
{
alert(txt)
}
</script>
</head>
<body>
<form>
<input type="button"
onclick="myfunction('Hello')"
value="Call function">
</form>
<p>By pressing the button, a function with an argument will be called. The function will alert
this argument.</p>
</body>
</html>
<html>
<head>
<script type="text/javascript">
function myfunction(txt)
{
alert(txt)
}
</script>
</head>
<body>
<form>
<input type="button"
onclick="myfunction('Good Morning!')"
value="In the Morning">
<input type="button"
onclick="myfunction('Good Evening!')"
value="In the Evening">
</form>
<p>
When you click on one of the buttons, a function will be called. The function will alert
the argument that is passed to it.
</p>
</body>
</html>
下面是函数返回一个值
<html>
<head>
<script type="text/javascript">
function myFunction()
{
return ("Hello, have a nice day!")
}
</script>
</head>
<body>
<script type="text/javascript">
document.write(myFunction())
</script>
<p>The script in the body section calls a function.</p>
<p>The function returns a text.</p>
</body>
</html>
函数传入参数，并且返回值
<html>
<head>
<script type="text/javascript">
function product(a,b)
{
return a*b
}
</script>
</head>
<body>
<script type="text/javascript">
document.write(product(4,3))
</script>
<p>The script in the body section calls a function with two parameters (4 and 3).</p>
<p>The function will return the product of these two parameters.</p>
</body>
</html>
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