How to force input to only allow Alpha Letters?

问题:

using jQuery here, however unable to prevent numbers from being typed into the input field

http://codepen.io/leongaban/pen/owbjg

Input

<input type="text" name="field" maxlength="8"     title="Only Letters"     value="Type Letters Only"     onkeydown="return alphaOnly(event);"     onblur="if (this.value == '') {this.value = 'Type Letters Only';}"     onfocus="if (this.value == 'Type Letters Only') {this.value = '';}"/> 

jQuery

function alphaOnly(event) {    alert(event);    var key;    if (window.event) {     key = window.event.key;   } else if (e) {     key = e.which;   }   //var key = window.event.key || event.key;   alert(key.value);   return ((key >= 65 && key <= 90) || (key >= 95 && key <= 122));  } 

I've seen plenty of examples here on how to restrict to only Numbers, and I'm using the correct key codes for a-z and A-Z. Do you see what I'm doing wrong?

回答1:

The property event.key gave me an undefined value. Instead, I used event.keyCode:

function alphaOnly(event) {   var key = event.keyCode;   return ((key >= 65 && key <= 90) || key == 8); }; 

Note that the value of 8 is for the backspace key.

回答2:

Rather than relying on key codes, which can be quite cumbersome, you can instead use regular expressions. By changing the pattern we can easily restrict the input to fit our needs. Note that this works with the keypress event and will allow the use of backspace (as in the accepted answer). It will not prevent users from pasting 'illegal' chars.

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> <label>    Test input:    <input id="my-field" type="text"> </label>

回答3:

On newer browsers, you can use:

<input type="text" name="country_code"      pattern="[A-Za-z]" title="Three letter country code"> 

You can use regular expressions to restrict the input fields.

回答4:

<input type="text" name="field" maxlength="8"     onkeypress="return onlyAlphabets(event,this);" />  function onlyAlphabets(e, t) {             try {                 if (window.event) {                     var charCode = window.event.keyCode;                 }                 else if (e) {                     var charCode = e.which;                 }                 else { return true; }                 if ((charCode > 64 && charCode < 91) || (charCode > 96 && charCode < 123))                     return true;                 else                     return false;             }             catch (err) {                 alert(err.Description);             }         } 

回答5:

Nice one-liner HTML only:

 <input type="text" id='nameInput' onkeypress='return ((event.charCode >= 65 && event.charCode <= 90) || (event.charCode >= 97 && event.charCode <= 122) || (event.charCode == 32))'> 

回答6:

<input type="text" name="name" id="event" onkeydown="return alphaOnly(event);"   required />   function alphaOnly(event) {   var key = event.keyCode;`enter code here`   return ((key >= 65 && key <= 90) || key == 8); }; 

文章来源: How to force input to only allow Alpha Letters?