Repeat Character N Times

Question

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.

Answer 1

Array(10).fill('a').join('')

Although the most voted answer is a bit more compact, with this approach you don't have to add an extra array item.

Answer 2

/**  
 * Repeat a string `n`-times (recursive)
 * @param {String} s - The string you want to repeat.
 * @param {Number} n - The times to repeat the string.
 * @param {String} d - A delimiter between each string.
 */

var repeat = function (s, n, d) {
    return --n ? s + (d || "") + repeat(s, n, d) : "" + s;
};

var foo = "foo";
console.log(
    "%s\n%s\n%s\n%s",

    repeat(foo),        // "foo"
    repeat(foo, 2),     // "foofoo"
    repeat(foo, "2"),   // "foofoo"
    repeat(foo, 2, "-") // "foo-foo"
);

Answer 3

Can be used as a one-liner too:

function repeat(str, len) {
    while (str.length < len) str += str.substr(0, len-str.length);
    return str;
}

Answer 4

These days, the repeat string method is implemented almost everywhere. (It is not in Internet Explorer.) So unless you need to support older browsers, you can simply write:

"a".repeat(10)

Before repeat, we used this hack:

Array(11).join("a") // create string with 10 a's: "aaaaaaaaaa"

(Note that an array of length 11 gets you only 10 "a"s, since Array.join puts the argument between the array elements.)

Simon also points out that according to this jsperf, it appears that it's faster in Safari and Chrome (but not Firefox) to repeat a character multiple times by simply appending using a for loop (although a bit less concise).

Answer 5

In a new ES6 harmony, you will have native way for doing this with repeat. Also ES6 right now only experimental, this feature is already available in Edge, FF, Chrome and Safari

"abc".repeat(3) // "abcabcabc"

And surely if repeat function is not available you can use old-good Array(n + 1).join("abc")

Answer 6

An alternative is:

for(var word = ''; word.length < 10; word += 'a'){}

If you need to repeat multiple chars, multiply your conditional:

for(var word = ''; word.length < 10 * 3; word += 'foo'){}

NOTE: You do not have to overshoot by 1 as with word = Array(11).join('a')