JavaScript validation: regex to validate numbers with comma

Question

How do I use JavaScript regex to validate numbers like this?

1. 1,000
2. 1,000.00
3. 1000.00
4. 1000

I tried this (the string used should not match):

test('2342342342sdfsdfsdf');

function test(t)
{
    alert(/\d{1,3}(,\d{3})*(\.\d\d)?|\.\d\d/.test(t));
}

but still gives me true.

Answer 1

If you want to test if the complete input string matches a pattern, then you should start your regex with ^ and end with $. Otherwise you are just testing if the input string contains a substring that matches the given pattern.

• ^ means "Start of the line"
• $ means "End of the line"

In this case it means you have to rewrite you regex to:

/^(\d{1,3}(,\d{3})*(\.\d\d)?|\.\d\d)$/

If you would omit the extra parentheses, because otherwise the "|" would have lower precedence than the ^ and $, so input like "1,234.56abc" or "abc.12" would still be valid.

Answer 2

I'm not sure what you mean by validate. But this might work.

//console.log is used in firebug.
var isNumber = function( str ){
    return !isNaN( str.toString().replace(/[,.]/g, '') );
}
console.log( isNumber( '1,000.00' ) === true );
console.log( isNumber( '10000' ) === true );
console.log( isNumber( '1,ooo.00' ) === false );
console.log( isNumber( 'ten' ) === false );
console.log( isNumber( '2342342342sdfsdfsdf') === false );

Answer 3

try this

var number = '100000,000,000.00';
var regex = /^\d{1,3}(,?\d{3})*?(.\d{2})?$/g;
alert(regex.test(number));