JS - Regex for number without leading zero, or just zero

Question

I am trying to write a regular expression for currency (no commas or $ signs or periods; just integers), but I am hitting a wall.

I need a the number (as a string) to m

Answer 1

Use the following regex:

/^(?:[1-9][0-9]*|0)$/

Details

• ^ - start of string
• (?: - start of an alternation group:
  • [1-9][0-9]* - a digit from 1 to 9 and then any 0+ digits
  • | - or
  • 0 - a 0
• ) - end of the group
• $ - end of the string.

See the regex demo.

JS demo:

var regex = /^(?:[1-9][0-9]*|0)$/;
var testCases = ['0', '12345', '0123', '456'];
for (var i in testCases) {
  var result = regex.test(testCases[i]); 
  console.log(testCases[i] + ': ' + result);      
}