how to use the union function from the underscore library in javascript

The union function from the Underscore library in JavaScript allows you to create an array of unique values, in order, from a combination of two or more arrays. It preserves the order of the arrays as they are passed in.

Here's an example usage of the union function:

index.tsx
const _ = require('underscore');

const arr1 = [1, 2, 3, 4];
const arr2 = [3, 4, 5, 6];
const arr3 = [5, 6, 7, 8];

const uniqueArr = _.union(arr1, arr2, arr3);

console.log(uniqueArr); // Output: [1, 2, 3, 4, 5, 6, 7, 8]
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In this example, we're using the union function to create a new array called uniqueArr that contains all of the unique values from arr1, arr2, and arr3. We pass each array as an argument to the union function, separated by commas.

The resulting output is [1, 2, 3, 4, 5, 6, 7, 8]. The union function has preserved the order of the arrays as well, so the resulting array is in the same order as the arguments that were passed in.