如何验证文本字段，使其只能包含四位数字 [英] How to validate a text field so it can only contain a four digit number

问题描述

我已经设法验证我的字段，所以它总是四位数，但我需要验证，以便它始终是一个数字。我尝试添加这段代码，但它无法正常工作。

I've managed to validate my field so it is always four digits, but i need to validate so that it is always a number. I tried adding this block of code but it doesn't work properly.

if (!(document.ExamEntry.cand.value.match(numbers))) {
    msg += "Only use numeric characters \n";
    document.ExamEntry.cand.focus();
    document.getElementById('cand').style.color = "red";
    result = false;
}  

这将允许四位数组合，如9a9a或！2＃3等。
我添加了这样的数字变量;

This will allow four digit combinations like 9a9a or !2#3 etc. I added the "numbers" variable like this;

var numbers = /[0-9]/;

进行此验证的更好方法是什么？

What is a better way of doing this validation?

推荐答案

假设你在这里得到你的价值

Let's say you get your value here

var val = document.ExamEntry.cand.value;

然后，如果你想让它成为4位数的东西，就这样做吧

Then if you want it to be something with 4 digits inside, just do this

var itIsNumber = /^\d{4}$/.test(val); // true if it is what you want

如果你希望它是1到4位的东西在里面，只需这样做

if you want it to be something with 1 to 4 digits inside, just do this

var itIsNumber = /^\d{1,4}$/.test(val); // true if it is what you want

此处有更多示例和详细信息 - > 正则表达式

more examples and details here --> Regular Expressions

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