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Lodash _.findLastIndex() Function - GeeksforGeeks

Last Updated : 02 Sep, 2024

Lodash _.findLastIndex() function is used to find the element from the right of the array. Therefore giving the index of the last occurrence of the element in the array.

findLastIndex(array, [predicate=_.identity], fromIndex);

• array: It is the original array.
• predicate: It is the function that iterates over each element.
• fromIndex: It is the index after which the search starts. If from Index is not given then by default it is n-1 where n is the length of the array.

It returns the index of the element if found else -1 is returned.

Example 1: In this example, we are getting the last index of element 2 that is present in the given array by the use of the lodash _.findLastIndex() function.

// Requiring the lodash library
const _ = require("lodash");

// Original array
let array1 = [4, 2, 3, 1, 4, 2]

// Using lodash.findLastIndex
let index = _.findLastIndex(array1, (e) => {
    return e == 2;
});

// Original Array
console.log("original Array: ", array1)

// Printing the index
console.log("index: ", index)

Output: 

Example 2: In this example, we are using the lodash _.findLastIndex() functionand getting "-1" as the element 1 is not present in the given array.

// Requiring the lodash library
const _ = require("lodash");

// Original array
let array1 = [4, 2, 3, 1, 4, 2]

// Using lodash.findLastIndex
let index = _.findLastIndex(array1, (e) => {
    return e == 1;
}, 2);

// Original Array
console.log("original Array: ", array1)

// Printing the index
console.log("index: ", index)

Output: 

Example 3: In this example, we are getting the last index of element 2 that is present in the given array of objects by the use of the lodash _.findLastIndex() function.

// Requiring the lodash library
const _ = require("lodash");

// Original array
let array1 = [
    { "a": 1, "b": 2 },
    { "b": 4 },
    { "a": 1 }
]

// Using lodash.findLastIndex
let index = _.findLastIndex(array1, (e) => {
    return e.b == 2;
}, 2);

// Original Array
console.log("original Array: ", array1)

// Printing the index
console.log("index: ", index)

Output: 

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