Regexp for floating number

Question

I found this regexp for validating floats. But I cant see how 2-1 will accepted. The below evaluates to true. I can't use parseFloat because I need to be able to accept "," instead of "." also. I wrote re2, same result though.

var re1 = new RegExp("^[-+]?[0-9]*\.?[0-9]+$");
console.log(re1.test("2-1"));

var re2 = new RegExp("^([0-9]+)\.([0-9]+)$");
console.log(re2.test("2-1"));

Stefan · Accepted Answer · 2012-07-10 07:53:47Z

3

If you generate the regex using the constructor function, you have to to escape the backslash, i.e. \ becomes \\:

var re1 = new RegExp("^[-+]?[0-9]*\\.?[0-9]+$");

Another option is to use the literal syntax which doesn't require escaping:

var re1 = /^[-+]?[0-9]*\.?[0-9]+$/

answered Jul 10, 2012 at 7:53

Stefan

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Daedalus · Accepted Answer · 2012-07-10 07:46:56Z

3

Sometimes when you create a regex string, you even have to escape the backslash; this can of course be done with a backslash, so the final regex looks something like "\\.*", etc.

Doing this, I was able to get the correct results, as seen here:

var re1 = new RegExp("^[-+]?[0-9]*\\.?[0-9]+$");
console.log(re1.test("2-1"));

var re2 = new RegExp("^([0-9]+)\\.([0-9]+)$");
console.log(re2.test("2-1"));

console.log(re1.test("2.1"));
console.log(re2.test("2.1"));

answered Jul 10, 2012 at 7:46

Daedalus

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azhrei · Accepted Answer · 2012-07-10 07:44:27Z

0

What about replacing a comma (",") with a period (".") and then using parseFloat?

answered Jul 10, 2012 at 7:44

azhrei

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