The _.frequencies() method takes an array and returns a mapping object whose keys are the values of the array’s elements and values are counts of that key appeared in that array.
Syntax:
_.frequencies( array );
Parameters: This method accepts a single parameter as mentioned above and described below:
- array: The given array from which mapping is to be created.
Return Value: This method returns a created mapping object.
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 –save.
Example 1:
Javascript
// Defining underscore contrib variable var _ = require('underscore-contrib'); // Array var array = ["Geeks", "Geeks", "GFG", "Computer_Science_Portal", "Geeks", "GFG"]; var obj = _.frequencies(array); console.log("Original Array : ", array); console.log("Generated Mapping Object: ", obj); |
Output:
Original Array : [ 'Geeks', 'Geeks', 'GFG',
'Computer_Science_Portal', 'Geeks', 'GFG' ]
Generated Mapping Object: { Geeks: 3, GFG: 2,
Computer_Science_Portal: 1 }
Example 2: For an empty array, an empty object is created.
Javascript
// Defining underscore contrib variable var _ = require('underscore-contrib'); // Array var array = []; var obj = _.frequencies(array); console.log("Original Array : ", array); console.log("Generated Mapping Object: ", obj); |
Output:
Original Array : []
Generated Mapping Object: {}
Example 3: This method works fine with integer array.
Javascript
// Defining underscore contrib variable var _ = require('underscore-contrib'); // Array var array = [1,1,1,1,1,1,3,3,3,4,4, 4,5,5,5,6,6,6,6,7,7,]; var obj = _.frequencies(array); console.log("Original Array : ", array); console.log("Generated Mapping Object: ", obj); |
Output:
Original Array : [
1, 1, 1, 1, 1, 1, 3,
3, 3, 4, 4, 4, 5, 5,
5, 6, 6, 6, 6, 7, 7
]
Generated Mapping Object: { '1': 6, '3': 3, '4':
3, '5': 3, '6': 4, '7': 2 }
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