如何防止keydown上的数字输入？ [英] How to prevent number input on keydown?

问题描述

我要防止在textfield上的 keydown事件上输入数字，并运行自定义处理函数。这是问题

• e.target.value 尚未投影到目标值


• e.keyCode 取决于键盘类型，语言布局，Fn或Shift键


• String.fromCharCode（e.keyCode）不可靠，至少在我的键盘（捷克qwerty）


• w3规范表示 e.keyCode 是一个旧属性，建议 e.char




那么如何在文本字段中显示之前捕获数字输入？

解决方案

使用 keypress 事件。它是唯一的关键事件，它将通过大多数浏览器中的 属性和（混淆地） keyCode / code>属性。使用它，您可以有条件地抑制基于键入的字符的 keypress 事件。但是，这不会帮助您阻止用户在包含数字字符的文本中粘贴或拖动，因此您仍需要某种额外的验证。





我最喜欢的引用JavaScript关键事件： http://unixpapa.com/js/key.html

  textBox.onkeypress = function（e）{
e = e || window.event; 
 var charCode =（typeof e.which ==undefined）？ e.keyCode：e.which; 
 var charStr = String.fromCharCode（charCode）; 
 if（/\d/.test(charStr））{
 return false; 
} 
}; 
  




I want to prevent number input on keydown event on textfield and run custom handler function. Here are the issues

• e.target.value is useless since the key value is not projected into the target value yet
• e.keyCode for number depends on keyboard type, language layout, Fn or Shift key
• String.fromCharCode(e.keyCode) is not reliable, at least on my keyboard (Czech qwerty)
• w3 specification says e.keyCode is a legacy attribute and suggests e.char instead, but it is not implemented in browsers yet

So how to catch the number input before it appears in the textfield?

解决方案

Use the keypress event instead. It's the only key event which will give you information about the character that was typed, via the which property in most browsers and (confusingly) the keyCode property in IE. Using that, you can conditionally suppress the keypress event based on the character typed. However, this will not help you prevent the user from pasting or dragging in text containing numeric characters, so you will still need some kind of extra validation.

My favourite reference for JavaScript key events: http://unixpapa.com/js/key.html

textBox.onkeypress = function(e) {
    e = e || window.event;
    var charCode = (typeof e.which == "undefined") ? e.keyCode : e.which;
    var charStr = String.fromCharCode(charCode);
    if (/\d/.test(charStr)) {
        return false;
    }
};

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