Repeat a string in JavaScript a number of times

user_131640 0
Viewed 348483

In Perl I can repeat a character multiple times using the syntax:

$a = "a" x 10; // results in "aaaaaaaaaa"

Is there a simple way to accomplish this in Javascript? I can obviously use a function, but I was wondering if there was any built in approach, or some other clever technique.

character repeat javascript string
25 Answers

Just for the fun of it, here is another way by using the toFixed(), used to format floating point numbers.

By doing

(0).toFixed(2)
(0).toFixed(3)
(0).toFixed(4)

we get

0.00
0.000
0.0000

If the first two characters 0. are deleted, we can use this repeating pattern to generate any repetition.

function repeat(str, nTimes) {
  return (0).toFixed(nTimes).substr(2).replaceAll('0', str);
}

console.info(repeat('3', 5));
console.info(repeat('hello ', 4));

user_6078740

Right pads with zeros with no arrays or loops. Just uses repeat() using ES6 2015, which has wide support now. Left pads if you switch the concatenation.

function pad(text, maxLength){ 
  var res = text + "0".repeat(maxLength - text.length);
  return res;
}

console.log(pad('hello', 8)); //hello000
user_10908020

this is how you can call a function and get the result by the helps of Array() and join()

function repeatStringNumTimes(str, num) {
  // repeat after me
  return num > 0 ? Array(num+1).join(str) : "";
}

console.log(repeatStringNumTimes("a",10))

user_82029740

I realize that it's not a popular task, what if you need to repeat your string not an integer number of times?

It's possible with repeat() and slice(), here's how:

String.prototype.fracRepeat = function(n){
  if(n < 0) n = 0;
  var n_int = ~~n; // amount of whole times to repeat
  var n_frac = n - n_int; // amount of fraction times (e.g., 0.5)
  var frac_length = ~~(n_frac * this.length); // length in characters of fraction part, floored
  
  return this.repeat(n) + this.slice(0, frac_length);
}

And below a shortened version:

String.prototype.fracRepeat = function(n){
   if(n < 0) n = 0;
   return this.repeat(n) + this.slice(0, ~~((n - ~~n) * this.length));
}

var s = "abcd";
console.log(s.fracRepeat(2.5))

user_29636520 
String.prototype.repeat = function (n) { n = Math.abs(n) || 1; return Array(n + 1).join(this || ''); };

// console.log("0".repeat(3) , "0".repeat(-3))
// return: "000" "000"
user_48483790
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