based on index of array add items to array in object

Question

I am scraping a website and have an array of numbers that I am looping over:

const arr = [1,2,3,1,2,4,5,6,7];

they correspond to win/lose/draw for different teams:

i.e.

1st item in array is won, second is draw, third is loss, fourth is won, fifth is draw, sixth is loss etc.

How can I loop through these so I have something like the following:

const teams = [{
  won: 1,
  draw: 2,
  lost: 3
 },{ 
  won: 1,
  draw: 2,
  lost: 4
 },{
  won: 5,
  draw: 6,
  lost: 7
}];

I tried something like the following but it didn't work as I expected.

   const arr = [1, 2, 3, 1, 2, 4, 5, 6, 7];

const newArr = [];

arr.forEach((item, index => {
   if (index % 0 === 0) {
     newArr.push({
       won: item
     });

   } else if (index % 1 === 0) {
     newArr.push({
       draw: item
     });
   } else {
     newArr.push({
       lost: item
     });
    }
 });

You need to read up on what % does, index % 1 means the remainder when index is divided by 1, which is always 0 (for non-negative integers). — Nick is tired
– Nick is tired, Commented Jun 10, 2018 at 21:50
Start with a syntax free example "Uncaught SyntaxError: missing ) after argument list" — Mark Schultheiss
– Mark Schultheiss, Commented Jun 10, 2018 at 21:53

CertainPerformance · Accepted Answer · 2018-06-10 21:48:46Z

2

Unfortunately, using the array methods like forEach won't work well because you need to consolidate multiple array elements into a single object. It's possible, but it would be a bit confusing. It might be clearer if you use a for loop:

const arr = [1,2,3,1,2,4,5,6,7];
const teams = [];
for (let i = 0; i < arr.length; i += 3) {
  teams.push({
    won: arr[i],
    draw: arr[i + 1],
    lost: arr[i + 2],
  });
}

console.log(teams);

answered Jun 10, 2018 at 21:48

CertainPerformance

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1 Comment

Bergi Over a year ago

+1. Alternatively, use a inChunksOf3 helper function and loop over the results of that.

user835611 · Accepted Answer · 2018-06-10 21:48:02Z

1

You want

index % 3 === 0; // 0, 3, 6, ...
index % 3 === 1; // 1, 4, 7, ...
index % 3 === 2; // 2, 5, 8, ...

answered Jun 10, 2018 at 21:48

user835611

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1 Comment

Mark Schultheiss Over a year ago

On right track or not, produce the final example desired for better answer.

Ivan · Accepted Answer · 2018-06-10 21:52:07Z

1

You can loop over your array but only consider every third element by using i+=3:

let teams = [];
function teamStats(won, draw, lost){
  return {won, draw, lost};
}
for(let i = 0; i < arr.length; i+=3){
  teams.push(teamStats(arr[i], arr[i+1], arr[i+2]));
}

edited Jun 10, 2018 at 21:52

Ivan

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answered Jun 10, 2018 at 21:49

eltonkamami

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