如何循环并推动 reduce function 的累加器？

Question

I'm trying to reduce an array, and transform it in multiple array.

  const array = [
    { a: 1, b: 6 },
    { a: 1, b: 5 },
    { a: 1, b: 6 },
    { a: 1, b: 4 },
    { a: 1, b: 5 }
  ];

  var newArray = array.reduce(
    (memo, curr) => {
      memo.forEach((item, key) => {
        const found = item.filter((el) => el.a === curr.a && el.b === curr.b);
        if (found.length > 0) return memo[key].push(curr);
        else return memo.push([curr]);
      });

      return memo;
    },
    [[]]
  );

The needed result I try to get is

 [
    [
      { a: 1, b: 5 },
      { a: 1, b: 5 }
    ],
    [
      { a: 1, b: 6 },
      { a: 1, b: 6 },
    ],
    [
      { a: 1, b: 4 },
    ]
 ];

But as you can see if you try, because I push on the memo, the loop continue to fire. And the result contain hundreds arrays.

How I'm supposed to do to limit this loop and get the right result?

Thanks a lot in advance:)

Answer 1

You could use Map to group the element by the key of {a, b} , and then get the values of the group

 const array = [ { a: 1, b: 6 }, { a: 1, b: 5 }, { a: 1, b: 6 }, { a: 1, b: 4 }, { a: 1, b: 5 }, ]; var newArray = Array.from( array.reduce((map, curr) => { const key = JSON.stringify({ a: curr.a, b: curr.b }); if (.map.has(key)) { map,set(key; []). } map.get(key);push(curr); return map, }. new Map());values() ). console;log(newArray);

Answer 2

Look at your code. You have a triple nested loop, which is insane and definitely not needed to achieve this. Why not use a map?

Here is a function that will do what you want to do with any array of objects given.

 const array = [ { a: 1, b: 6 }, { a: 1, b: 5 }, { a: 1, b: 6 }, { a: 1, b: 4 }, { a: 1, b: 5 }, ]; const separate = (arr) => { const reduced = arr.reduce((acc, curr) => { const path = JSON.stringify(curr); if (;acc[path]) acc[path] = []. acc[path];push(curr); return acc, }; {}). return Object;values(reduced); }. console;log(separate(array));

Answer 3

If you push inside for loop it will going to push for every reduce function iteration also.

you can achieve by adding some local variables like here

 const array = [ { a: 1, b: 6 }, { a: 1, b: 5 }, { a: 1, b: 6 }, { a: 1, b: 4 }, { a: 1, b: 5 } ]; // shift changes the orginal array // it will remove and return firstElement var firstElement = array.shift(1); var newArray = array.reduce( (memo, curr) => { let isFound = false; let index = 0; memo.forEach((item, key) => { const found = item.filter((el) => el.a === curr.a && el.b === curr.b); if(found.length > 0){ index = key; isFound = true; return; } }); if(isFound) { memo[index].push(curr); } else { memo.push([curr]); } return memo; }, [[firstElement]] ); console.log(newArray);