Determine the index of items within an array of objects in Lodash where a boolean property is set to true

Question

Determine the index of items within an array of objects in Lodash where a boolean property is set to true

I am new to using lodash after transitioning from C# where I occasionally used LINQ. I have discovered that lodash can be utilized for querying in a LINQ-style manner, but I'm struggling to retrieve the indexes of items in an array of objects with a boolean property set to true using lodash. Can anyone offer some assistance?

My initial attempt:

var indexOfItems = _.find(arrayOfItems, (item) => 
  (item.booleanProperty === true));

However, when I try:

var indexItems: number[] = [];
indexItems = _.times(
  arrayOfItems.length,
  _.find(arrayOfItems, (item) => (item.booleanProperty === true));

The second line doesn't compile either.

Thank you!

javascript typescript lodash

Answer 1

Answer №1

Using plain JavaScript is all you need to accomplish the same task without relying on lodash.

const data = [{
    booleanProperty: false
  },
  {
    booleanProperty: true
  },
  {
    booleanProperty: false
  },
  {
    booleanProperty: true
  },
  {
    booleanProperty: false
  }
];

const indexItems = data.map((item, index) => item.booleanProperty === true ? index : null).filter((item) => item !== null);


console.log(indexItems)

Answer 2

Using plain JavaScript is all you need to accomplish the same task without relying on lodash.

const data = [{
    booleanProperty: false
  },
  {
    booleanProperty: true
  },
  {
    booleanProperty: false
  },
  {
    booleanProperty: true
  },
  {
    booleanProperty: false
  }
];

const indexItems = data.map((item, index) => item.booleanProperty === true ? index : null).filter((item) => item !== null);


console.log(indexItems)

Answer 3

Answer №2

If you're looking for a single index that meets the condition, you can utilize the findIndex method from either es6 or lodash

data.findIndex(a=>a.booleanProperty)

If you need all the indexes that satisfy your criteria, you have options. You can combine map and filter, or streamline the process with a single reduce. Here's an example using reduce:

data.reduce((r, a, i)=> (a.booleanProperty && r.push(i), r), [])

let data = [{"booleanProperty":false},{"booleanProperty":true},{"booleanProperty":false},{"booleanProperty":true},{"booleanProperty":false}];
    
let indexes = data.reduce((r, a, i)=> (a.booleanProperty && r.push(i), r), []);
  
console.log(indexes);

Answer 4

If you're looking for a single index that meets the condition, you can utilize the findIndex method from either es6 or lodash

data.findIndex(a=>a.booleanProperty)

If you need all the indexes that satisfy your criteria, you have options. You can combine map and filter, or streamline the process with a single reduce. Here's an example using reduce:

data.reduce((r, a, i)=> (a.booleanProperty && r.push(i), r), [])

let data = [{"booleanProperty":false},{"booleanProperty":true},{"booleanProperty":false},{"booleanProperty":true},{"booleanProperty":false}];
    
let indexes = data.reduce((r, a, i)=> (a.booleanProperty && r.push(i), r), []);
  
console.log(indexes);

Determine the index of items within an array of objects in Lodash where a boolean property is set to true

Answer №1

Answer №2

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