Workaround for not jet implemented String.padStart/padEnd

Had the need to fill a string with '0' at the end.

var len = 64;   
var sb = parseInt(1023).toString(2);
var sbl = sb.length;
var sbFixedLenStart = ('0').repeat((len-sbl)?(len-sbl):0) + sb;
var sbFixedLenEnd = sb + ('0').repeat((len-sbl)?(len-sbl):0);
console.log(sbFixedLenStart);
console.log(sbFixedLenEnd);

/* output
0000000000000000000000000000000000000000000000000000001111111111
1111111111000000000000000000000000000000000000000000000000000000
*/