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当用户点击递交按钮或点击单行文本输入框按下回车键后，表单递交到3w服务器之前就会发生onsubmit()事件，典型用法就是检查form表单收到数据的合法性和完整性,防止将不正确的数据传递给3w服务器如果 onsubmit 句柄返回 fasle，表单的元素就不会提交。如果该函数返回其他值或什么都没有返回，则表单会被提交。
<!DOCTYPE html>
<html lang="en" xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta charset="utf-8" />
<title></title>
<script language="javascript">
function dosubmit(frm) {
if (frm.mem_id.value.length != 6) {
alert("会员号必须是6位");
return false;
}
else {
var mem_value = frm.mem_id.value;
for (var i = 0; i < mem_value.length; i++) {
if (mem_value.charAt(i) < '0' ||
mem_value.charAt(i) > '9') {
alert("会员号只能是数字");
return false;
}
}
}
return true;
}
</script>
</head>
<body>
<form name="form1" target="_blank" method="post"
onsubmit="return dosubmit(this)">
<!--若提交成功，浏览器打开一个新的窗口-->
会员号码(6位数字):<input type="text" name="mem_id" />
<input type="submit" name="submit1" value="递交" />
</form>
</body>
</html>
<!DOCTYPE html>
<html lang="en" xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta charset="utf-8" />
<title></title>
<script language="javascript">
function dosubmit(frm) {
if (frm.mem_id.value.length != 6) {
alert("会员号必须是6位");
return false;
}
else {
var mem_value = frm.mem_id.value;
for (var i = 0; i < mem_value.length; i++) {
if (mem_value.charAt(i) < '0' ||
mem_value.charAt(i) > '9') {
alert("会员号只能是数字");
return false;
}
}
if (i == mem_value.length)
frm.submit();
}
return true;
}
</script>
</head>
<body>
<form name="form1" target="_blank" method="post"
onsubmit="dosubmit(this);return false">
<!--若提交成功，浏览器打开一个新的窗口-->
会员号码(6位数字):<input type="text" name="mem_id" />
<input type="submit" name="submit1" value="递交" />
</form>
</body>
</html>
<html>
<body>
<form id="myForm">
Firstname:
<input id="fname" type="text" value="Mickey" />
Lastname:
<input id="lname" type="text" value="Mouse" />
<input id="sub" type="button" value="Submit" />
</form>
<p>
Get the value of all the elements in the form:<br />
<script type="text/javascript">
var x = document.getElementById("myForm");
for (var i = 0; i < x.length; i++) {
document.write(x.elements[i].value);
document.write("<br />");
document.write(x.elements[i].type);
document.write("<br />");
}
</script>
</p>
</body>
</html>
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原文地址：http://blog.csdn.net/lindonglian/article/details/45116473
