Is there a way to prepend leading zeros to numbers so that it results in a string of fixed length? For example, 5
becomes "05"
if I specify 2 places.
This question is related to
javascript
text-formatting
number-formatting
UPDATE: Small one-liner function using the ES2017 String.prototype.padStart
method:
const zeroPad = (num, places) => String(num).padStart(places, '0')_x000D_
_x000D_
console.log(zeroPad(5, 2)); // "05"_x000D_
console.log(zeroPad(5, 4)); // "0005"_x000D_
console.log(zeroPad(5, 6)); // "000005"_x000D_
console.log(zeroPad(1234, 2)); // "1234"
_x000D_
Another ES5 approach:
function zeroPad(num, places) {
var zero = places - num.toString().length + 1;
return Array(+(zero > 0 && zero)).join("0") + num;
}
zeroPad(5, 2); // "05"
zeroPad(5, 4); // "0005"
zeroPad(5, 6); // "000005"
zeroPad(1234, 2); // "1234" :)
From https://gist.github.com/1180489
function pad(a, b){
return(1e15 + a + '').slice(-b);
}
With comments:
function pad(
a, // the number to convert
b // number of resulting characters
){
return (
1e15 + a + // combine with large number
"" // convert to string
).slice(-b) // cut leading "1"
}
You could extend the Number
object:
Number.prototype.pad = function(size) {
var s = String(this);
while (s.length < (size || 2)) {s = "0" + s;}
return s;
}
Examples:
(9).pad(); //returns "09"
(7).pad(3); //returns "007"
Just for fun (I had some time to kill), a more sophisticated implementation which caches the zero-string:
pad.zeros = new Array(5).join('0');
function pad(num, len) {
var str = String(num),
diff = len - str.length;
if(diff <= 0) return str;
if(diff > pad.zeros.length)
pad.zeros = new Array(diff + 1).join('0');
return pad.zeros.substr(0, diff) + str;
}
If the padding count is large and the function is called often enough, it actually outperforms the other methods...
function zfill(num, len) {return (Array(len).join("0") + num).slice(-len);}
Source: Stackoverflow.com