Solution to the problem that textarea cannot limit the number of words through the maxlength attribute_javascript skills

Textarea is called text area, also known as text area, which is a multi-line text input control with scroll bar. It is often used in submission forms on web pages. Unlike the single-line text box text control, it cannot limit the number of words through the maxlength attribute. For this reason, other methods must be found to limit it to meet the preset requirements.

The usual approach is to use #scripting language to limit the number of words entered in the textarea text field, which is simple and practical. Suppose we have a textarea with an ID of txta1. We can limit its keyboard input characters to 10 characters (Chinese characters or other small-angle characters) through the following code:

<script language="#" type="text/ecmascript"> 
window.onload = function() 
{ 
document.getElementById('txta1').onkeydown = function() 
{ 
if(this.value.length >= 10) 
event.returnValue = false; 
} 
} 
</script>

Its principle is to monitor the text area with the specified ID number through the keydown (keyboard key press) event. As you can imagine, it can only limit keyboard input if the user pastes the text in the clipboard through the right mouse button. , it cannot control the word count.

Input via keyboard, only 10 characters can be entered in the above text area. However, our goal was not achieved! Just copy some text and try pasting it with the right mouse button and see what happens.

You can find other JS scripts similar to the above on the Internet. No matter how excellent they are, their principles are the same. They monitor input in the text area through keyboard key operation events such as keydown, keyup or keypress. Prevent the right mouse button from being pasted. For this reason, if we must really limit the number of words in the textarea, we have to add another lock to the web page - disabling the right mouse button. This will undoubtedly cost extra, and it may also be a problem for the web page creator. Not necessarily willing to do it. In fact, there is a simpler way, using the onpropertychange attribute.

onpropertychange can be used to judge the value of a predetermined element. When the value of the element changes, the judgment event will be triggered. Only the value of the monitored element is concerned, avoiding the source of the input, so that it can be ideally Meet our word limit. It belongs to the category of JS and can be used nested in the form box area representative. The following is the code and effect style. You can test the input as above, and you will find that it really achieves the purpose: no matter what method is used to input, it can only input 100 Characters (Chinese characters or other Chinese characters):

Code:

<textarea onpropertychange="if(value.length>100) value=value.substr(0,100)" class="smallArea" cols="60" name="txta" rows="8"></textarea>

Of course, in order to be more secure, the background script that processes form data should also check the submitted data again. If the number of words exceeds the preset number, it will be processed accordingly, so as to achieve the purpose of truly limiting the number of words. . (End)

Another way to limit the number of input characters in textarea (including Chinese, only 10 can be input, and full ASCII code can input 20)

<script> 
function check() { 
var regC = /[^ -~]+/g; 
var regE = /\D+/g; 
var str = t1.value; 

if (regC.test(str)){ 
t1.value = t1.value.substr(0,10); 
} 

if(regE.test(str)){ 
t1.value = t1.value.substr(0,20); 
} 
} 
</script> 
<textarea maxlength="10" id="t1" onkeyup="check();"> 
</textarea>

There is another way:

function textCounter(field, maxlimit) { 
if (field.value.length > maxlimit){ 
field.value = field.value.substring(0, maxlimit); 
}else{ 
document.upbook.remLen.value = maxlimit - field.value.length; 
} 
}

<textarea name=words cols=19 rows=5 class=input1 onPropertyChange= "textCounter(upbook.words, 50) "> textarea> 
剩余字数: <input name=remLen type=text id= "remLen " style= "background-color: #D4D0C8; border: 0; color: red " value=50 size=3 maxlength=3 readonly>

function LimitTextArea(field){ 
maxlimit=200; 
if (field.value.length > maxlimit) 
field.value = field.value.substring(0, maxlimit);
}

<textarea cols=50 rows=10 name="comment" id="commentarea" onKeyDown="LimitTextArea(this)" onKeyUp="LimitTextArea(this)" onkeypress="LimitTextArea(this)" ></textarea>

title="The textarea width must less than 300 characters." When placed in the textarea, it prompts for the maximum number of bytes.

For example:

<textarea title="The textarea width must less than 300 characters." cols=50 rows=10 name="comment" id="commentarea" onKeyDown="LimitTextArea(this)" onKeyUp="LimitTextArea(this)" onkeypress="LimitTextArea(this)" ></textarea>