Basically what I'm trying to do is map this array and identify which objects satisfy a certain condition. The condition is: Get an object that has the highest value of a b and if you have two objects with the same value of a b, get the one that has the highest value of c. What is the best way to do this? Maybe reduce?

   const data = [
      {
        id: 1,
        a: 12,
        b: 75,
        c: 11,
      },
      {
        id: 2,
        a: 65,
        b: 14,
        c: 32,
      },
      {
        id: 3,
        a: 32,
        b: 23,
        c: 45,
      },
      {
        id: 4,
        a: 22,
        b: 1,
        c: 3,
      },
    ];

CodePudding user response：

A simple for loop should work. Loop through the array and if the current object's a b is greater than a stored object, overwrite the stored object with the current loop object - checking c if necessary.

CodePudding user response：

A simple for loop would be great

const data = [
      {
        id: 1,
        a: 12,
        b: 75,
        c: 11,
      },
      {
        id: 2,
        a: 65,
        b: 14,
        c: 32,
      },
      {
        id: 3,
        a: 32,
        b: 23,
        c: 45,
      },
      {
        id: 4,
        a: 22,
        b: 1,
        c: 3,
      },
    ];
    
let index,
  cHigh = Number.MIN_SAFE_INTEGER,
  total = Number.MIN_SAFE_INTEGER;

for (let i = 0; i < data.length;   i) {
  const { a, b, c } = data[i];
  if (a   b > total) {
    total = a   b;
    index = i;
  } else if (a   b === total) {
    if (c > cHigh) {
      cHigh = c;
      index = i;
    }
  }
}
console.log(index);
console.log(data[index]);

CodePudding user response：

data.reduce((res, obj) => {
  if (!res) return obj

  const { a: resA, b: resB, c: resC } = res
  const { a, b, c } = obj

  const sumRes = resA   resB
  const sum = a   b
  
  if(sum > sumRes) return obj
  else if (sum === sumRes) return c > resC ? obj : res
  else return res

}, null)

I think that's pretty understandable.

We initialize the first result with the first index. And we make a simple comparison game

CodePudding user response：

Already a first naive reduce based approach which implements the OP's requirements and constraints almost literally does exactly what the OP is asking for.

In case one does not provide an initial value to the reducer, this reducing callback function gets passed the first two array items at its first invocation time. The function is supposed to return a value which, with any following iteration step, will be passed as the very functions 1st argument alongside the currently processed array item (which is the 2nd argument).

Thus for the OP's use case one just needs to implement the correct comparison which always ensures the expected return value ...

function getItemWithHighestTotal(result, item) {
  const resultTotal = result.a   result.b;
  const itemTotal = item.a   item.b;
  return (
    ((resultTotal > itemTotal) && result) ||
    ((resultTotal < itemTotal) && item) ||
    ((result.c < item.c) && item) ||
    // OP did not define the clause where
    // even both `c` values are equal.
    result
  );
}

console.log(
  [{
    id: 1,
    a: 12,
    b: 75,
    c: 11,
  }, {
    id: 2,
    a: 65,
    b: 14,
    c: 32,
  }, {
    id: 3,
    a: 32,
    b: 23,
    c: 45,
  }, {
    id: 4,
    a: 22,
    b: 1,
    c: 3,
  }].reduce(getItemWithHighestTotal)
);
console.log(
  [{
    id: 1,
    a: 12,
    b: 75,
    c: 11,
  }, {
    id: 2,
    a: 65,
    b: 14,
    c: 32,
  }, {
    id: 3,
    a: 32,
    b: 23,
    c: 45,
  }, {
    id: 4,
    a: 22,
    b: 1,
    c: 3,
  }, {
    id: 5,
    a: 75,
    b: 12,
    c: 12,
  }].reduce(getItemWithHighestTotal)
);

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