I want to extend the following regex to negative numbers.

this.value = this.value.replace(/[^0-9\.]/g, "");

I tried adding minus sign doing something like this, (/[^-0-9.]/g, "") but this allows minus sign to be entered anywhere in the number. I want to allow only one occurance of the minus sign at the beginning of the number. Later occurances of minus should be ignored.

Please help.

I want to extend the following regex to negative numbers.

this.value = this.value.replace(/[^0-9\.]/g, "");

I tried adding minus sign doing something like this, (/[^-0-9.]/g, "") but this allows minus sign to be entered anywhere in the number. I want to allow only one occurance of the minus sign at the beginning of the number. Later occurances of minus should be ignored.

Please help.

• javascript
• jquery
• regex

5 Answers 5

Uh, replacing every non-number character makes that a bit harder - it's like "negating" the regex. What I came up with is a negative lookahead, preventing a minus - which would be matched by [^0-9.] - from beeing matched if it is in the beginning of the string (using a start anchor):

….replace(/(?!^-)[^0-9.]/g, "")

Why RegEx? How about:

var temp = parseFloat(this.value)
this.value = isNaN(temp) ? "" : temp;

This should also work:

var temp = +this.value;
this.value = isNaN(temp) ? "" : temp;

Put your dash outside of the character class:

this.value = this.value.replace(/^-?[^0-9\.]/g, "");

The regex in provided by you is faulty for the positive numbers itself as it will convert "100+200=300" to "100200300".

I suggest you try this: someString.match(/-?[\d]+.?[\d]*/);

It is only to put the negative symbol in front of the 0

this.value = this.value.replace(/[^-0-9\.]/g, "");