提交数据四种方式

1，form提交

<form method="post" action="index.php">
    <input type="text" name="username" value="" />
    <input type="submit" value="提交">
</form>

2，js提交

<form method="post" action="index.php" id="login">
    <input type="text" name="username" id="username" value="" />
    <input type="button" value="提交" onclick="return validate();">
</form>
<script>
function validate() {
    var username = document.getElementsByName('username')[0].value;
    //var username = document.getElementById('username').value;
    if (username == '') {
        return false;
    }
    document.getElementById('login').submit();
}
</script>

• return vallidate();这里的return可有可无

• type="button" 这里不能用submit，如果用的话，会提交两次

3，form onsubmit()

<form method="post" action="index.php" onsubmit="return validate();">
    <input type="text" name="username" id="username" value="" />
    <input type="submit" value="提交">
</form>
<script>
function validate() {
    var username = document.getElementsByName('username')[0].value;
    //var username = document.getElementById('username').value;
    if (username == '') {
        return false;
    }
}
</script>

onsubmit必须加上return

4，ajax提交
......