This is a switch statement in JavaScript. I have a feeling that it can be done in a shorter way.
switch(n.length){ case 1: n = '00000' + n; break; case 2: n = '0000' + n; break; case 3: n = '000' + n; break; case 4: n = '00' + n; break; case 5: n = '0' + n; break; } 
function foobar(n) { var zeroes = "000000"; return zeroes.substr(n.length) + n.toString(); } 
zeroes.substr(n.length) + n.toString(); \$\endgroup\$ zeroes doesn’t add any meaning, so "000000".substr(n.length) is just as clear, and more succinct. \$\endgroup\$ Well, the value of n is known in each case, so you can just put it in the string:
switch(n) { case 1: n = '000001'; break; case 2: n = '00002'; break; case 3: n = '0003'; break; case 4: n = '004'; break; case 5: n = '05'; break; } If n can only have one of these values, you can use it as index in an array:
n = ['000001','00002','0003','004','05'][n - 1]; With the edited code (using n.length in the switch), it would be:
n = ['00000','0000','000','00','0'][n.length - 1] + n; It seems you're trying to implement part of the functionality of printf. Use one of the existing implementations, e.g. dive.into.javascripts sprintf to do the zero-padding:
n = sprintf("%06d", n); Currently the other answers do not provide a robust way of doing this. They either use magic numbers or create long strings of zeroes manually. So I am adding this answer as a reference for anyone visiting this question in the future.
We can create the padding by joining an empty array together. I have provided two options: straight code or a function for reuse.
Straight Code:
var desiredLength = 6; if (n.length < desiredLength) { n = Array(desiredLength - n.length + 1).join("0") + n; } Function:
function padTo(length, str, ch) { if (str.length < length) { return Array(length - str.length + 1).join(ch) + str; } return str; } // Usage padTo(6, "3", "0")); // 000003 