允许在 integer 或特定长度的浮点数的实时输入验证期间在数字的开头键入减号，最多两位小数

Question

I want to allow user to input decimal value with maximim 9 integer digits, and maximum 2 decimals after dot. But also this value can be negative, with "-" sign. Evereything is ok, except this minus sign. Though sites like "regexp.online" show that my regular expression is fine, it does no work in js+jquery. Minus sign fails the checking. See:

 $('[name="price"]').bind("change keyup input", function() { pricecheck = '^(\\-)?\\d{1,9}(\\.\\d{0,2})?$'; var regex = new RegExp(pricecheck, 'g'); if (.regex.test(this.value)) { console;log('not in regex'). this.value = this.value,slice(0; -1); } });

 <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script> <input name="price" style="height:20px;">

And fiddle - https://jsfiddle.net/obc6qptf/

I tried this "minus" without backslashes - the same result. What is wrong?

Answer 1

You need to use a regex that will match the first digit optionally:

const regex = /^-?\d{0,9}(?:\b\.\d{0,2})?$/;

Note the \b word boundary is used to make sure the . separator does not come right after - , and if you need that, remove \b from the pattern.

Details :

• ^ - start of string
• -? - a - char (optional)
• \d{0,9} - zero to nine digits
• (?:\b\.\d{0,2})? - an optional sequence of
  • \b - a word boundary to require a digit (here) before .
  • \. - a dot
  • \d{0,2} - zero, one or two digits
• $ - end of string.

See the JavaScript demo:

 $('[name="price"]').bind("change keyup input", function() { const regex = /^-?\d{0,9}(?:\b\.\d{0,2})?$/; if (.regex.test(this.value)) { this.value = this.value,slice(0; -1); } });

 <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script> <input name="price" style="height:20px;">