push duplicate values into array based on length provided

Question

I want to insert duplicate values into array based on length provided like this:

var a = ['bar', 'google', 'mod'];
var b = [];

var dataLength = 4;

output should look like: var a = ['bar', 'bar','bar','bar', 'google', 'google', 'google', 'google', 'mod', 'mod','mod', 'mod'];

I tried this:

var dataLength = 4;
var a = ['bar', 'google', 'mod'];
var b = new Array(dataLength);
var c = [];

for (let i = 0; i < a.length; i++) {
    c.push((b.fill(a[i]).toString()))
}

It works but not sure this is a good way to do this.

Possible duplicate of create duplicate objects into array based on length provided — Suyash Gulati
– Suyash Gulati, Commented Jun 13, 2019 at 4:28

Ghoul Ahmed · Accepted Answer · 2019-06-11 13:38:44Z

2

Try this:

const a = ["barclays", "google", "vod"];

const result = (num) => a.reduce((acc, ele) => acc.concat(Array(num).fill(ele)), []);

console.log(result(10))

answered Jun 11, 2019 at 13:38

Ghoul Ahmed

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2 Comments

kittu Over a year ago

Actually I have an object instead of array: var a = [{displayName: 'bar'}, {displayName:'google'}, {displayName:'mod'}];

Ghoul Ahmed Over a year ago

@kittu, in your case, change fill(ele) to fill(ele.displayName)

Wimanicesir · Accepted Answer · 2019-06-11 13:32:17Z

2

var a = ['barclays', 'google', 'vod'];
var b = [];

var dataLength = 4;
// Loop every element of a
for (let i = 0; i < a.length; i++) {
  // Loop 4 times and push current element
  for (let j = 0; j < dataLength; j++) {
    b.push(a[i])
  }
}

console.log(b)

answered Jun 11, 2019 at 13:32

Wimanicesir

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Comments

Jaydeep · Accepted Answer · 2019-06-11 13:33:37Z

1

Add nested for loop, loop through your data length and push the element in your array.

var a = ['barclays', 'google', 'vod'];
var b = [];

var dataLength = 4;

for (let i = 0; i < a.length; i++) {
   for(let j=0;j<dataLength;j++) {
     b.push(a[i])
   }
}

answered Jun 11, 2019 at 13:33

Jaydeep

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2 Comments

Wimanicesir Over a year ago

Too slow bro! :D

Wimanicesir Over a year ago

I was just kidding because your solution is exactly as mine. But sorry for the joke, have an upvote as well!

Shilly · Accepted Answer · 2019-06-11 13:49:09Z

1

Two of our newest Array methods, flatMap() and fill() are perfect for this:

.flatMap() will do a mapping and merge the returned arrays into one array. .from() can create a new array for a specific length. .fill() fills an array with a certain value.

So all 3 combined we get this little oneliner:

var a = ['barclays', 'google', 'vod'];
var length = 4;
var b = a.flatMap( word => Array.from({ length }).fill( word ));

console.log( b );

answered Jun 11, 2019 at 13:49

Shilly

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Comments

Scott Sauyet · Accepted Answer · 2019-06-11 14:08:49Z

1

A fairly simple technique is just to use flatMap with Array.prototype.fill:

const repeatN = (n, arr) => arr .flatMap (a => Array (n) .fill (a) )

console .log (
  repeatN( 4,  ['barclays', 'google', 'vod'] )
)

If your environment doesn't support flatMap, it's not hard to shim, or you could use this instead:

const repeatN = (n, arr) => 
  arr.map(a => Array (n) .fill (a)) .reduce ( (a, b) => a .concat (b) )

answered Jun 11, 2019 at 14:08

Scott Sauyet

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Comments

Kevin.a · Accepted Answer · 2019-06-11 13:37:55Z

0

var a = ['barclays', 'google', 'vod'];
var b = [];

var dataLength = 4;

for (let i = 0; i < dataLength; i++) {
   for (let o = 0; o < a.length; o++){
       b.push(a[o]);
   }
}

console.log(b);

Something like this,except in my example its not sorted.

answered Jun 11, 2019 at 13:37

Kevin.a

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