The_.partitionBy() method takes an array and a function and hence generates a partitioned array based on the conditions of the given function.
Syntax:
_.partitionBy(array, function)
Parameters:
- array: The given array from which the partitioned array is to be created.
- function: The function containing the conditions for an array to be partitioned.
Return Value: This method returns a newly created partitioned array.
Note: This will not work in normal JavaScript because it requires the underscore.js contribute library to be installed.
underscore.js contrib library can be installed using:
npm install underscore-contrib –save
Example 1: In this example, we will create a partitioned array of even and odd elements using this method.
javascript
// Defining underscore contrib variableconst _ = require('underscore-contrib');// Arraylet array = [1, 2, 3, 2, 1, 1, 5, 6, 6, 6, 7, 8, 9, 9, 10];// Creating partitioned arraylet p_arr = _.partitionBy(array, _.isOdd);console.log("Original Array : ", array);console.log("Partitioned Array: ", p_arr); |
Output:
Original Array : [ 1, 2, 3, 2, 1, 1, 5, 6, 6, 6, 7, 8, 9, 9, 10 ] Partitioned Array: [ [ 1 ], [ 2 ], [ 3 ], [ 2 ], [ 1, 1, 5 ], [ 6, 6, 6 ], [ 7 ], [ 8 ], [ 9, 9 ], [ 10 ] ]
Example 2: In this example, we will create a partitioned array of all identical elements.
javascript
// Defining underscore contrib variableconst _ = require('underscore-contrib');// Arraylet array = [1, 2, 3, 2, 1, 1, 5, 6, 6, 6, 7, 8, 9, 9, 10];// Creating partitioned arraylet p_arr = _.partitionBy(array, _.identity);console.log("Original Array : ", array);console.log("Partitioned Array: ", p_arr); |
Output:
Original Array : [ 1, 2, 3, 2, 1, 1, 5, 6, 6, 6, 7, 8, 9, 9, 10 ] Partitioned Array: [ [ 1 ], [ 2 ], [ 3 ], [ 2 ], [ 1, 1 ], [ 5 ], [ 6, 6, 6 ], [ 7 ], [ 8 ], [ 9, 9 ], [ 10 ] ]
Example 3: In this example, we will create a partitioned array of all negative and positive numbers.
javascript
// Defining underscore contrib variableconst _ = require('underscore-contrib');// Arraylet array = [1, 2, 3, 2, -1, -1, 5, 6, -6, -6, -7, -8, 9, 9, 10];// Creating partitioned arraylet p_arr = _.partitionBy(array, function (val) { return val > 0});console.log("Original Array : ", array);console.log("Partitioned Array: ", p_arr); |
Output:
Original Array : [ 1, 2, 3, 2, -1, -1, 5, 6, -6, -6, -7, -8, 9, 9, 10 ] Partitioned Array: [ [ 1, 2, 3, 2 ], [ -1, -1 ], [ 5, 6 ], [ -6, -6, -7, -8 ], [ 9, 9, 10 ] ]
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