Javascript adding zeros to the beginning of a string (max length 4 chars)

Question

var number = 1310;

should be left alone.

var number = 120;

should be changed to \"0120\";

var num         


        

Answer 1

Nate as the best way I found, it's just way too long to read. So I provide you with 3 simples solutions.

1. So here's my simplification of Nate's answer.

//number = 42
"0000".substring(number.toString().length, 4) + number;

2. Here's a solution that make it more reusable by using a function that takes the number and the desired length in parameters.

function pad_with_zeroes(number, len) {
  var zeroes = "0".repeat(len);
  return zeroes.substring(number.toString().length, len) + number;
}

// Usage: pad_with_zeroes(42,4);
// Returns "0042"

3. Here's a third solution, extending the Number prototype.

Number.prototype.toStringMinLen = function(len) {
  var zeroes = "0".repeat(len);
  return zeroes.substring(self.toString().length, len) + self;
}

//Usage: tmp=42; tmp.toStringMinLen(4)