How to use Javascript array.find() with two conditions?

Question

I need to check if any object in an array of objects has a type: a AND if another has a type: b

I initially did this:

const myObjects = objs.filter(attr => attr.type === 'a' || attr.type === 'b');

But the code review complained that filter will keep going through the entire array, when we just need to know if any single object meets either criteria.

I wanted to use array.find() but this only works for a single condition.

Is there anyway to do this without using a for loop?

upog · Accepted Answer · 2020-04-24 04:42:12Z

4

you can pass two condition as given below

[7,5,11,6,3,19].find(attr => {
    return (attr > 100 || attr %2===0);
});
6

[7,5,102,6,3,19].find(attr => {
    return (attr > 100 || attr %2===0);
});
102

answered Apr 24, 2020 at 4:42

upog

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Comments

hnOsmium0001 · Accepted Answer · 2020-04-26 19:58:14Z

-1

Updated answer:

It's not possible to shortcircuit js's builtin functions that does what you want, so you will have to use some kind of loop:

let a;
let b;
for (const elm of objs) {
  if (!a && elm === 'a') {
    a = elm;
  }
  if (!b && elm === 'b') {
    b = elm;
  }
  const done = a && b;
  if (done) break;
}

Also you should consider if you can record a and b when producing the array if that's possible.

Oiginal answer:

`find` works just like `filter` where it takes a predicate, returns the first element that the predicate returns `true`. If I understood your question correctly, you can just replace the `filter` with `find` and it will return at the first occurance:
const myObject = objs.find(attr => attr.type === 'a' || attr.type === 'b');
Also notice your provided snippet is wrong for what you described: `filter` returns an array but you only wanted one element. so you should add `[0]` to the filter expression if you want to use it.

edited Apr 26, 2020 at 19:58

answered Apr 24, 2020 at 4:44

hnOsmium0001

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4 Comments

codemon Over a year ago

Won't this stop as soon as it finds an element that has a? meaning it will never look for b if it has found a

hnOsmium0001 Over a year ago

@codemon Can you phrase your problem more clearly then? Based on your description I assumed you want the first 'a' or 'b'. Or do you want the first 'a' and the first 'b'?

codemon Over a year ago

I want the first 'a' or the first 'b' or both if both exist.

hnOsmium0001 Over a year ago

@codemon At that point I think the answer is "no": You will have to write a for loop then, and in my opinion well-written for loops are very readable. See edited answer for example.

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