The _.dropWhile() method takes an array and a function and hence returns an array in which elements are dropped from the original array for which the function returns true.
Note: values are dropped until the function returns false, after a false value no changes to the original value are made.
Syntax:
_.dropWhile(array, function)
Parameters: This method accepts two parameters as mentioned above and described below:
- array: The given array from which dropped array is created.
- function: The function containing the conditions for elements to be dropped.
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:
npm install underscore-contrib
Example 1: In this example, we will create an array with all positive values dropped.
Javascript
// Defining underscore contrib variableconst _ = require('underscore-contrib');// Arraylet array = [11, 21, 43, 34, 12, -1];// Getting dropped array using dropWhile() methodlet d_array = _.dropWhile(array, function (x) { return x > 0;});console.log("Array : ", array);console.log("Dropped Array : ", d_array); |
Output:
Array : [ 11, 21, 43, 34, 12, -1 ] Dropped Array : [ -1 ]
Example 2: In this example, we will create an array with all negative values dropped.
Javascript
// Defining underscore contrib variableconst _ = require('underscore-contrib');// Arraylet array = [-1, -21, -43, 34, 12, -1];// Getting dropped array using dropWhile() methodlet d_array = _.dropWhile(array, function (x) { return x < 0;});console.log("Array : ", array);console.log("Dropped Array : ", d_array); |
Output: negative values are dropped until a positive value comes.
Array : [ -1, -21, -43, 34, 12, -1 ] Dropped Array : [ 34, 12, -1 ]
Example 3: In this example, we will create an array with 0 values dropped until the function returns false.
Javascript
// Defining underscore contrib variableconst _ = require('underscore-contrib');// Arraylet array = [0, 0, 0, 0, 0, -1, -21, -43, 34, 12, -1];// Getting dropped array using dropWhile() methodlet d_array = _.dropWhile(array, function (x) { return x == 0;});console.log("Array : ", array);console.log("Dropped Array : ", d_array); |
Output:
Array : [ 0, 0, 0, 0, 0, -1, -21, -43, 34, 12, -1 ] Dropped Array : [ -1, -21, -43, 34, 12, -1 ]