How to find if a specific key is true in Array of objects

Question

I have this array and I want to to get a boolean(true) if there is a 'three' that is equal to 9

myArr = [ { apple: 6, basket: [ { one: 1, two: 2, three: 3 }, { one: 4, two: 5, three: 6 } ] }, { apple: 9, basket: [ { one: 1, two: 2, three: 3 }, { one: 4, two: 5, three: 9 } ] } ]

What I tried:

enter code here

this.myArr.forEach( data => {
      if(data.basket.filter(cur => cur.one === 0 || cur.three === 9)) {
       console.log('true')
      }
    })

This always logs true for some reason I don't know why.

CertainPerformance · Accepted Answer · 2020-05-19 15:27:17Z

4

.filter will always return an array of elements which pass the test, and arrays are truthy. Even if no elements pass the test, the array will still be truthy:

const arr = [1, 2, 3].filter(() => false);
if (arr) {
  console.log('truthy');
}

Use .some instead, to see if there is at least one element which passes the test:

const myArr = [{
  apple: 6,
  basket: [{
    one: 1,
    two: 2,
    three: 3
  }, {
    one: 4,
    two: 5,
    three: 6
  }]
}, {
  apple: 9,
  basket: [{
    one: 1,
    two: 2,
    three: 3
  }, {
    one: 4,
    two: 5,
    three: 9
  }]
}]

myArr.forEach(data => {
  if (data.basket.some(cur => cur.one === 0 || cur.three === 9)) {
    console.log('true');
  }
});

answered May 19, 2020 at 15:27

CertainPerformance

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2 Comments

Cray Over a year ago

Wouldn't some() stop looping if it finds a value that match the condition? Thank you very much

CertainPerformance Over a year ago

Yes, but that's what you want, right? As you said: I want to to get a boolean(true) if there is a 'three' that is equal to 9

Siva Kondapi Venkata · Accepted Answer · 2020-05-19 16:37:26Z

0

filter returns to array and use find which will return matched item or null when no match.

In you code, Just change from filter to find will work fine.

const myArr = [
  {
    apple: 6,
    basket: [
      { one: 1, two: 2, three: 3 },
      { one: 4, two: 5, three: 6 }
    ]
  },
  {
    apple: 9,
    basket: [
      { one: 1, two: 2, three: 3 },
      { one: 4, two: 5, three: 9 }
    ]
  }
];

const items = myArr.map(data =>
  data.basket.find(cur => cur.one === 0 || cur.three === 9) ? "true" : "false"
);

console.log(items);

answered May 19, 2020 at 16:37

Siva Kondapi Venkata

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