Javascript 检查文本字段值长度
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checking text field value length
提问by droidus
I am trying to see if the text field length is at least a certain length. here is my code:
我想看看文本字段长度是否至少是某个长度。这是我的代码：
<form name="form2" id="form2" onsubmit="return validate()">
length 4: <input type="text" name = "t" id="t" />
<input type="button" name="submit" value="submit" />
</form>
<script>
function validate() {
document.write("good");
submitFlag = true;
if(document.form2.t.value.length!=4){
submitFlag=false;
alert("ivalid length - 4 characters needed!");
}
return submitFlag;
}
</script>
when I click submit, nothing happens.
当我点击提交时，没有任何反应。
回答by Geoff Warren
Change your submit button to type="submit". The form is never getting submitted so the validate function isn't being called.
将您的提交按钮更改为 type="submit"。表单永远不会被提交，因此不会调用验证函数。
回答by daker
The input type needs to be "submit"
输入类型需要为“提交”
<form name="form2" id="form2" onsubmit="return validate()">
length 4: <input type="text" name = "t" id="t" />
<input type="submit" name="submit" value="submit" /> <!--INPUT TYPE MUST BE SUBMIT -->
</form>
<script>
function validate() {
document.write("good");
submitFlag = true;
if(document.form2.t.value.length!=4){
submitFlag=false;
alert("ivalid length - 4 characters needed!");
}
return submitFlag;
}
</script>
回答by Jonathan Payne
You should also add a maxlength attribute to your text input, it'll help the user.
您还应该为文本输入添加一个 maxlength 属性，它会帮助用户。
<form name="form2" id="form2" onsubmit="return validate();">
<input type="text" name="t" id="t" maxlength="4"/>
<input type="submit" name="submit" value="submit"/>
</form>
<script type="text/javascript">
function validate()
{
if ( document.getElementById("t").value.length != 4 )
{
alert( "Invalid length, must be 4 characters" );
return false;
}
return true;
}
</script>
回答by Christopher Scott
You probably want greater than or equal to (>=), instead of not equal to (!=) if you want "at least a certain length"
如果您想要“至少某个长度”，您可能想要大于或等于 (>=)，而不是不等于 (!=)
回答by paislee
回答by Bergi
I've spotted various errors:
我发现了各种错误：
- don't use
document.write(), it will overwrite the currently open document form2is no property ofdocument. You may usedocument.forms.form2, butdocument.getElementById("t")is simpler here- Your expression doesn't check for "at least 4", it checks for "exactly 4".
- Your button won't submit anything. Change it to
<button type="submit">or<input type="submit" /> - you could specify a
pattern=".{4}"for the input or give it arequiredattribute
- 不要使用
document.write()，它会覆盖当前打开的文档 form2不是 的属性document。您可以使用document.forms.form2，但document.getElementById("t")这里更简单- 您的表达式不检查“至少 4”，它检查“正好 4”。
- 你的按钮不会提交任何东西。将其更改为
<button type="submit">或<input type="submit" /> - 您可以
pattern=".{4}"为输入指定一个或给它一个required属性
回答by scottheckel
There's a few issues that you have. 1) You need to make your input a submit button and 2) you need to remove your document.write()statement. Change your code to the following (or see this jsFiddle):
你有几个问题。1) 您需要将您的输入设为提交按钮 2) 您需要删除您的document.write()声明。将您的代码更改为以下内容（或查看此 jsFiddle）：
<form name="form2" id="form2" onsubmit="return validate()">
length 4: <input type="text" name = "t" id="t" />
<input type="submit" name="submit" value="submit" />
</form>
<script>
function validate() {
submitFlag = true;
if(document.form2.t.value.length!=4){
submitFlag=false;
alert("ivalid length - 4 characters needed!");
}
return submitFlag;
}
</script>????
You were pretty close, but you could use some clean-up on that code (Note: I did not provide any).
您非常接近，但是您可以对该代码进行一些清理（注意：我没有提供任何内容）。
