DOM（九）使用DOM设置文本框

1.控制用户输入的字符个数对于单行文本框和密码输入框，可以利用maxlength属性控制用户输入的字符个数。对于多行文本，maxlength为自定义属性，其值最多输入的字符的个数，在onkeyPRess事件发生时则调运返回LessThan()函数返回值，函数如下

<textarea name="comments" id="comments" cols="40" rows="4" maxlength="50" onekeypress ="return LessThan(this);"></textarea>

详细代码

<script language="javascript">function LessThan(oTextArea){//返回文本框字符个数是否符号要求的boolean值return oTextArea.value.length < oTextArea.getAttribute("maxlength");}</script><form method="post" name="myForm1" action="addInfo.aspx"><p><label for="name">请输入您的姓名:</label><input type="text" name="name" id="name" class="txt" value="姓名" maxlength="10"></p><p><label for="comments">我要留言:</label><br><textarea name="comments" id="comments" cols="40" rows="4" maxlength="50" onkeypress="return LessThan(this);"></textarea></p><p><input type="submit" name="btnSubmit" id="btnSubmit" value="Submit" class="btn"><input type="reset" name="btnReset" id="btnReset" value="Reset" class="btn"></p></form>

2.设置鼠标经过自动选择文本

首先是鼠标经过时自动聚焦 onmouSEOver = "this.focus"

其次是 onfocus = "this.select()"代码实例:

<form method="post" name="form1" id="form1" action="addInfo.aspx"><input type="text" name="name" id="name" class="txt" value="姓名" onmouseover="this.focus()" onfocus="this.select()"></form>

对于多个代码实例，可以使用以下代码进行聚焦

<script type="text/Javascript">            function myFocus() {                this.focus();            }            function mySelect() {                this.select();            }            window.onload = function() {                var oForm = document.forms["myForm1"];                oForm.name.onmouseover = myFocus;                oForm.name.onfocus = mySelect;            }        </script>            <form method="post" name="myForm1" action="addInfo.aspx">                <p>                    <label for="name">请输入您的姓名:</label>                    <input type="text" name="name" id="name" class="txt" value="姓名">                </p>                <p>                    <label for="passwd">请输入您的密码:</label>                    <input type="passWord" name="passwd" id="passwd" class="txt">                </p>                <p>                    <input type="submit" name="btnSubmit" id="btnSubmit" value="Submit" class="btn">                    <input type="reset" name="btnReset" id="btnReset" value="Reset" class="btn">                </p>            </form>