Lodash is a JavaScript library that works on the top of underscore.js. Lodash helps in working with arrays, strings, objects, numbers, etc.
The _.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.
Syntax:
findLastIndex(array, [predicate=_.identity], fromIndex);
Parameter:
- array: It is the original array.
- predicate: It is the function that iterates over each element.
- fromIndex: It is the index after which the searching starts. If from Index is not given then by default it is n-1 where n is the length of the array.
Return Value: It returns the index of the element if found else -1 is returned.
Note: Install lodash module by using command npm install lodash before using the code given below.
Example 1:
// 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: When an element is present in the array but the output is -1 because it is present after the from the index. Here fromIndex is 2.
// 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: When an array of objects is given.
// Requiring the lodash library const _ = require("lodash"); // Original array let array1 = [ { "a": 1, "b": 2 }, { "b": 4 }, { "a": 1 } ] // Using lodash.findLastIndex let index = lodash.findLastIndex(array1, (e) => { return e.b == 2; }, 2); // Original Array console.log("original Array: ", array1) // Printing the index console.log("index: ", index) |
Output:
