Disadvantages of String.padStart()
- works only in modern browsers and environments;
- don't care about negative
- works only on String primitives not a Number
(-4+'').padStart(7,'0')
"00000-4"Our Overengineering but less headache way:
/** ES2015+ -- ultra-fast
@param n <Number> what to pad left with
@param z <Number> (zeros :) ) width which pad to
@param s <String> (sign :) ) char to pad with, of course may be some like that 'oO'
@return <String>
@example
np(7, 15, 'oO')
// ==> "oOoOoOoOoOoOoO7"
np(-1005007, 20)
// ==> "-00000000000001005007"
*/
const np = (n, z = 2, s= '0') =>
(n+'').length <= z ? (['','-'])[+(n<0)] + (s.repeat(z) + Math.abs(n)).slice(-1*z) : n + '';
/** v2, do the same but can work in carton boxes
*/
function np2(n, z, s) {
var z= z || 2, s = s || '0';
function rpt(z,s) {acc='';for(i=0;i<z;i++) acc+=s; return acc}
if ( (n+'').length <= z )
return (['','-'])[+(n<0)] + (rpt(z,s) + Math.abs(n)).slice(-1*z)
else
return n + '';
}Features:
- cares about negative numbers
- cares about length -- don't cut just pads
- works with Numbers
- v2 works in legacy trash cans even in MS IE 3.1 and Rhino
- have a short way (defaults)