How to duplicate a string multiple times and add a random array value to it

Question

I want to return the string 'street' 5 times and for it to add 4 random letters from the 'letters' array for each time so that they're different for each street.

let letters = ['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z'];

let a = {
    street: 'Street 21 ',
    do: function() {
        for (let i = 0; i < 4; i++) {
            this.street += letters[Math.floor(Math.random() * letters.length)];     
        };
    }
}

My code adds 4 random letters from the array to street already, but im not sure how to duplicate it multiple times, I can't just use .repeat() as I also need it to be in new lines.

Expected output:

Street 21 JIDX
Street 21 UYXZ
Street 21 ABCD
Street 21 EFGH
Street 21 KLMN

@MichaelBianconi yes just added it

vcosiekx
– vcosiekx

2019-08-15 16:24:54 +00:00
Commented Aug 15, 2019 at 16:24 — vcosiekx
– vcosiekx, Commented Aug 15, 2019 at 16:24
Is that output a string or array of strings?

Michael Bianconi
– Michael Bianconi

2019-08-15 16:27:41 +00:00
Commented Aug 15, 2019 at 16:27 — Michael Bianconi
– Michael Bianconi, Commented Aug 15, 2019 at 16:27

user1984 · Accepted Answer · 2019-08-15 16:46:33Z

1

I'd use map and join. That's easier to read, IMHO, and more functional.

const letters = ['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z'];

const result = new Array(5)
  .fill('Street 21')
  .map(
    el =>
      el +
      ' ' +
      new Array(4)
        .fill('')
        .map(el => el + letters[Math.floor(Math.random() * letters.length)])
        .join('')
  )
  .join('\n');
console.log(result);

edited Aug 15, 2019 at 16:46

answered Aug 15, 2019 at 16:36

user1984

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2 Comments

vcosiekx Over a year ago

And how can i make for each line it adds 3 random letters from the letters array instead of just one?

user1984 Over a year ago

Ahh, sorry, didn't see that you needed three letters added.

Liad Yogev · Accepted Answer · 2019-08-15 16:39:21Z

1

Considering that you want the output as a string:

let letters = ['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z'];

let a = {
    street: 'Street 21 ',
    do: function() {
        var fullString = "";
        const multipleAmount = 5; // the amount of streets you want to generate.
        let streetString = this.street;

        for (let j = 0; j < multipleAmount; j++) {
           for (let i = 0; i < 4; i++) {
               streetString  += letters[Math.floor(Math.random() * letters.length)];     
           };
           fullString += streetString;
           fullString += "\n"; // new line
           streetString = this.street;
        }
        this.street = fullString;
    }
}

edited Aug 15, 2019 at 16:39

answered Aug 15, 2019 at 16:29

Liad Yogev

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2 Comments

vcosiekx Over a year ago

Just tried running that and this is the output i received: Street 21 FStreet 21 AStreet 21 QStreet 21 Z Street 21 ZStreet 21 IStreet 21 BStreet 21 K Street 21 KStreet 21 IStreet 21 XStreet 21 J Street 21 UStreet 21 TStreet 21 LStreet 21 B Street 21 HStreet 21 QStreet 21 QStreet 21 T 5 lines of street 21 repeated 4 times in each line, not sure how to show it properly in comments

Liad Yogev Over a year ago

@vcosiekx my bad, fixed now :)

Olivier Boissé · Accepted Answer · 2019-08-15 16:48:11Z

1

const letters = [
  'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 
  'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z'
];

const street = 'Street 21 ';

function generateRandomLetter() {
  return letters[Math.floor(Math.random() * letters.length)];
}

function generateNRandomLetters(n) {
  return Array(n)
    .fill()
    .map(generateRandomLetter)
    .reduce((s, l) => `${s}${l}`,'');
}

function generateResult() {
  const getStreetValue = () => `${street}${generateNRandomLetters(4)}`       

  return Array(4)
   .fill()
   .map(getStreetValue)
   .reduce((r, s) => `${r}\n${s}`, getStreetValue());
}

const result = generateResult();

console.log(result);

edited Aug 15, 2019 at 16:48

answered Aug 15, 2019 at 16:38

Olivier Boissé

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