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10 JavaScript string methods you should know

Frugence Fidel on July 12, 2018

This post is originally published to my blog. In this post I will summarize 10 javascript string methods you should at least known according to me...

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ItsASine (Kayla) • Jul 13 '18

repeat exists? :o

I've been doing new Array(52).join('a'); to make a string of 52 as, but I could have just used 'a'.repeat(52)... now I need to make a little commit to update that.

The other day I even ranted about how nice Python's 'a' * 52 would have been.

Frugence Fidel • Jul 13 '18 • Edited

They are not same

 const first = new Array(2).join('a');
 console.log(first); // 'a'

 const second = 'a'.repeat(2);
 console.log(second); // 'aa'

 // new Array(52).join('a') will not print 52 a's, print 51 a's
 const aLength = new Array(52).join('a').length;
 console.log(aLength); // 51

ItsASine (Kayla) • Jul 13 '18 • Edited

Oops, you're right! Typo on my part :) For the sake of my E2E tests, I actually think repeat would be easier to read.

it('displays an error for too many characters', function() {
    relevantPage.middleInitial.sendKeys('a'.repeat(2)); // clearly shows that 2 is considered too many

    expect(relevantPage.middleInitialTooLongMessage.getText()).toEqual('Middle initial is too long');
});

Frugence Fidel • Jul 14 '18

Actually repeat is easy to read

If you want to make string of 52 a's with repeat is so easy

  const a = 'a'.repeat(52);
  console.log(a); // "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
  console.log(a.length); // 52

siddharthray • Jul 28 '18

Array index starts from 0 which means it will print 52 times.

diek • Jan 25 '19

Yass, and since join acts as 'glue', using 'a' as glue for 52 nothings will print 'a' 51 times. Give it a try ;)

Patrick Cole • Jul 20 '18

Great list of methods for Strings. I would just like to highlight that String.startsWith() and String.repeat() are ES2015+ String.endsWith() is ES6+, so polyfill accordingly to support edge cases.