create duplicate objects into array based on length provided

Question

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

var a = [{displayName: 'bar'}, {displayName:'google'}, {displayName:'mod'}];;
var dataTypesLength= 4;

Output should be like:

var a = [{displayName: 'bar'},{displayName: 'bar'},{displayName: 'bar'},{displayName: 'bar'}, {displayName:'google'},{displayName:'google'},{displayName:'google'},{displayName:'google'}, {displayName:'mod'}, {displayName:'mod'}, {displayName:'mod'}, {displayName:'mod'}];

I tried this:

a = a.flatMap( word => Array.from({ dataTypesLength}).fill( word ));

but I am getting typescript error saying: Argument of type '{ dataTypesLength: any; }' is not assignable to parameter of type 'ArrayLike<{}>'. Object literal may only specify known properties, and 'dataTypesLength' does not exist in type 'ArrayLike<{}>'

Start with something simple and something you can cope with: eg with 2 nested loops, one iterates the a, the other iterates 1..4 and pushes items from a. This is a straightforward and naive solution. As long as you have it working - you can see if you can turn it into composition of functions. — zerkms
– zerkms, Commented Jun 12, 2019 at 4:22
That object is not an array like - it has a dataTypesLength property, not a length property... — VLAZ
– VLAZ, Commented Jun 12, 2019 at 4:24

Syed mohamed aladeen · Accepted Answer · 2019-06-12 04:39:50Z

2

Just loop the array of objects and use fill to get your result.

var a = [{displayName: 'bar'}, {displayName:'google'}, {displayName:'mod'}];
var dataTypesLength= 4;
var arr=[];
function fillArray(value, len) {
  return Array(len).fill(value);
}
for (var i=0; i<a.length; i++){
  var b = fillArray(a[i],dataTypesLength);
  arr.push(...b);
}
console.log(arr);

answered Jun 12, 2019 at 4:39

Syed mohamed aladeen

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Comments

Suyash Gulati · Accepted Answer · 2019-06-12 04:59:39Z

2

You can use this (single line solution):

a.reduce((acc,x)=>{ acc.push(...new Array(dataTypesLength).fill(x)); return acc;}, [])

Explaination :

Reducing the input array starting from empty array []
For every element creating a new array with length dataTypesLength and filling all the new array with the current element new Array(dataTypesLength).fill(x)
Spread the new created array and push it into accumulator array acc.push(...new Array(dataTypesLength).fill(x))
Return the accumulator array

answered Jun 12, 2019 at 4:59

Suyash Gulati

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Vineesh · Accepted Answer · 2019-06-12 05:17:14Z

2

You can use map with Object.assign so that each object will have independent reference

var a = [{displayName: 'bar'}, {displayName:'google'}, {displayName:'mod'}];
var dataTypesLength= 4;

a= a.map(obj => { return Array(dataTypesLength).fill(null).map( e => Object.assign({}, obj)) }).flat();
console.log(a)

edited Jun 12, 2019 at 5:17

answered Jun 12, 2019 at 4:49

Vineesh

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2 Comments

Syed mohamed aladeen Over a year ago

one small thing. each set of objects are in different arrays. I think OP needs in same array

Vineesh Over a year ago

We can use Array.flat(). Updated the answer

Harish · Accepted Answer · 2019-06-12 04:30:00Z

0

you can try reduce

var a = [{displayName: 'bar'}, {displayName:'google'}, {displayName:'mod'}];;
var dataTypesLength= 4;

a  = a.reduce(
(f,obj ) => {
var dup = new Array(dataTypesLength); 
f.push(...dup.fill(obj));
return f;
}, [] )

answered Jun 12, 2019 at 4:30

Harish

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