Sorry, in advance if the title is unclear, but it's hard to describe it in a words.

What I have:

const obj = {
 a: 5,
 b: 3,
 c: 0,
 d: 9
}

What I want to have:

const arr = [[a, 5] ,[b, 3]]

Basically, I try to write a function that return me array of entries, but it has too meet requirements:

• don't want objects when values is equal to 0
• sum of values must be less than 10

First point is easy for me and I can do it by

Object.entries(obj).filter(([k, v])=> v !== 0)

but I can't handle with the second one.

May I use reduce here?

CodePudding user response：

You can use a closure and an IIFE to store the sum

Object.entries(obj).filter((() => {
  let sum = 0;
  return ([k, v]) => { sum  = v; return v !== 0 && sum < 10; }; 
})());

Examples:

const obj = {
 a: 5,
 b: 3,
 c: 0,
 d: 9
}

const arr = Object.entries(obj).filter((() => {
  let sum = 0;
  return ([k, v]) => { sum  = v; return v !== 0 && sum < 10; }; 
})());
console.log(arr);

const obj2 = {a: 0, b: 0, c: 8, d: 0, e: 1, f: 5};

const arr2 = Object.entries(obj2).filter((() => {
  let sum = 0;
  return ([k, v]) => { sum  = v; return v !== 0 && sum < 10; }; 
})());
console.log(arr2);

const obj3 = {a: 12};

const arr3 = Object.entries(obj3).filter((() => {
  let sum = 0;
  return ([k, v]) => { sum  = v; return v !== 0 && sum < 10; }; 
})());
console.log(arr3);

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CodePudding user response：

@jabaa's answer is great and you should accept it.

Just to confirm your intuition, you could have used reduce, but it would get rather complicated:

const obj = {
 a: 5,
 b: 3,
 c: 0,
 d: 9
}

const result = Object.entries(obj).reduce(
  (o, newPair) => {
     o.sum  = newPair[1];
     newPair[1] !== 0 && o.sum < 10 && o.pairs.push(newPair);
     return o;
  },
  {
     sum: 0,
     pairs: []
  }
).pairs;

console.log(result)

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