Javascript仅在ASP.NET TextBox中输入带有三位小数的正或负十进制数

Question

I have one TextBox in my UserControl. Here I want enter only positive or negative decimal number with three decimal places. For example like below: 128.324, -23.453, 10, 0.453, -2, 2.34, -5.34 The TextBox should not allow to enter other characters. How to do this using JavaScript? I am not good enough in JavaScript.

Answer 1

A regular expression to check content would be something like:

var re = /^[+-]?[\d,]+(\.\d{3})?$/;

but that will not enforce a comma for thousands, only allow it somewhere in the integer part. Note that in some countries, a comma is used for the decimal point.

Answer 2

If you validate on change your should be alright. Make sure you also validate any data that is sent to the server, on the server, since any data can be sent no matter how you try to validate it with JS:

var input = document.getElementById('tehinput');
input.onchange = function(){
    var val = this.value, sign = '';
    if(val.lastIndexOf('-', 0) === 0){
        sign = '-';
        val = val.substring(1);
    }
    var parts = val.split('.').slice(0,2);
        if(parts[0] && parseInt(parts[0], 10).toString() !== parts[0]){
        parts[0] = parseInt(parts[0], 10);
        if(!parts[0])
            parts[0] = 0;
    }
    var result = parts[0];
    if(parts.length > 1){
        result += '.';
        if(parts[1].length > 3 || 
          parseInt(parts[1], 10).toString() !== parts[1]){
              parts[1] = parseInt(parts[1].substring(0,3), 10);
              if(!parts[1])
                  parts[1] = 0;
        }
        result += parts[1];
    }
    this.value = sign+result;
}

JSFiddle