The _.keep() method takes an array and a function and hence returns an array generated which keeps only true values based on the conditions of the function.
Syntax:
_.keep(array, function)
Parameters:
- array: The given array from which the keep array is created.
- function: The function containing the conditions for elements to be kept.
Return Value: This method returns a newly created array.
Note: This will not work in normal JavaScript because it requires the underscore.js contrib library to be installed.
underscore.js contrib library can be installed using:Â
npm install underscore-contrib –save
Example 1: In this example, we will create an array by keeping all positive values.
javascript
// Defining underscore contrib variableconst _ = require('underscore-contrib');// Arraylet array = [-1, -21, -43, 34, 12, -1];// Getting keep array using keep() methodlet k_array = _.keep(array, function (x) {Â Â Â Â if (x > 0) {Â Â Â Â Â Â Â Â return x;Â Â Â Â }});console.log("Original Array : ", array);console.log("Generated keep Array : ", k_array); |
Output:
Original Array : [ -1, -21, -43, 34, 12, -1 ] Generated keep Array : [ 34, 12 ]
Example 2: In this example, we will create an array by keeping all negative values.
javascript
// Defining underscore contrib variableconst _ = require('underscore-contrib');// Arraylet array = [-1, -21, -43, 34, 12, -1];// Getting keep array using keep() methodlet k_array = _.keep(array, function (x) {Â Â Â Â if (x < 0) {Â Â Â Â Â Â Â Â return x;Â Â Â Â }});console.log("Original Array : ", array);console.log("Generated keep Array : ", k_array); |
Output:
Original Array : [ -1, -21, -43, 34, 12, -1 ] Generated keep Array : [ -1, -21, -43, -1 ]
Example 3: In this example, we will create an array by keeping all multiples of 5.
javascript
// Defining underscore contrib variableconst _ = require('underscore-contrib');// Arraylet array = [-1, -25, -43, 10, 125, -1];// Getting keep array using keep() methodlet k_array = _.keep(array, function (x) {Â Â Â Â if (x % 5 == 0) {Â Â Â Â Â Â Â Â return x;Â Â Â Â }});console.log("Original Array : ", array);console.log("Generated keep Array : ", k_array); |
Output:
Original Array : [ -1, -25, -43, 10, 125, -1 ] Generated keep Array : [ -25, 10, 125 ]
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