javascript限制文本输入字符 [英] javascript limit text input characters

问题描述

我想将文本框的输入字符限制为[a-z0-9_-]。但是，无论何时此按钮如退格键和箭头键都不起作用。我在本网站和其他网站上发现了一些尝试，但要么它们在所有浏览器上都无法正常工作，要么使用黑名单。例如， W3Schools网站示例黑名单列出数字。有没有办法使用白名单（上面的那个），仍然允许像退格，箭头，家庭，结束等键？或者我是否必须添加与我想要允许的键匹配的每个键码？我这样做（为简单起见，这是缩短的。）

I am wanting to restrict the input characters for a text box to [a-z0-9_-]. However whenever if do this buttons like backspace and the arrow keys don't work. I have found some attempts on this website and others but either they don't work properly on all browsers or they use a black list. For example the W3Schools website example black lists numbers. Is there a way to use white list (the one above) and still allow keys like backspace, arrows, home, end etc? Or do i have to add everyone of the key codes that match the keys i want to allow? I do something like this (this is shortened for simplicity).

编辑 - 添加代码

 <input type="text" onkeypress="return checkInput();">
    function checkInput(){
        return /[a-z0-9_-]/gi.test(String.fromCharCode(window.event.keyCode));
    }

谢谢

推荐答案

只需将示例中的正则表达式更改为以下内容：

Just change the regex in the example to something like this:

numcheck = /[^a-z0-9_-]/;

或者更好的是，避免双重否定：

Or better yet, avoid the double negative with:

numcheck = /[a-z0-9_-]/;
return numcheck.test(keychar);

然后你可以查找退格键等的密码，并检查它们：

Then you can look up the keycodes of backspace, etc. and check for them too:

if (keychar === 8) return true;
...

甚至将它们放入你的正则表达式中：

Or even put them in your regex:

numcheck = /[a-z0-9_\x08-]/;

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