The _.unionWith() method accepts comparator which is invoked to compare elements of arrays. The order of result values is determined from the first array in which the value occurs. The comparator is invoked with two arguments: (arrVal, othVal).
Syntax:
_.unionWith(array, [comparator])
Parameters: This method accepts two parameters as mentioned above and described below:
- array: This parameter holds the array to inspect.
- [comparator]: This parameter holds the comparator invoked per element.
Return Value: This method is used to return the new array of combined values.
Example 1: Here, const _ = require(‘lodash’) is used to import the lodash library into the file.
Javascript
// Requiring the lodash library  const _ = require("lodash");    // Original array var objects = [{ 'a': 1, 'b': 2 }]; var others = [{ 'b': 2 }];   // Use of _.unionWith() method let gfg = _.unionWith(objects, others, _.isMatch);         // Printing the output  console.log(gfg) |
Output:Â
[{'a': 1, 'b': 2 }, { 'b': 2}]
Example 2: Â
Javascript
// Requiring the lodash library  const _ = require("lodash");    // Original array var objects = [{ 'x': 1, 'y': 2 }, { 'x': 2, 'y': 1 }]; var others = [{ 'x': 1, 'y': 1 }, { 'x': 1, 'y': 2 }];   // Use of _.unionWith() method let gfg = _.unionWith(objects, others, _.isEqual);         // Printing the output  console.log(gfg) |
Output:
[{ 'x': 1, 'y': 2 }, { 'x': 2, 'y': 1 }, { 'x': 1, 'y': 1 }]
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