DEV Community: cortim

Quick Tip: Find if array has duplicates

cortim — Fri, 22 Mar 2024 00:26:05 +0000

Given the array below, which contains duplicates:
const arr = [1, 2, 5, 2, 6, 1];

We can perform the following check:
const hasDuplicates = (new Set(arr)).size !== arr.length;

The result is true, indicating the presence of duplicates in the array.

Quick Tip: Flattening a multidimensional array

cortim — Fri, 22 Mar 2024 00:14:13 +0000

Array with one level of nesting:
const arr = [[1, 2, 3], ["foo", "bar"], [4, "baz"]]

To make it flat:
const flatten = arr.flat() // [1, 2, 3, "foo", "bar", 4, "baz"]

Here, we're using the flat(depth) method, where depth defaults to 1. Therefore, flat() is equivalent to flat(1).
We can flatten arrays with as many levels of nesting as needed. If unsure about the number of levels, we can always use flat(Infinity), which will flatten all nested arrays.

Quick Tip: Array of consecutive integers

cortim — Thu, 21 Mar 2024 23:55:18 +0000

Instead of using a traditional for loop, try this:
const arr = [...Array(4).keys()] // [0, 1, 2, 3]

Quick Tip: Array of unique values

cortim — Thu, 21 Mar 2024 23:42:57 +0000

Original array with duplicates:
const nonUnique = [1, 4, 1, 3, 3]

Array with unique values only:
const uniqueArr = [...new Set(nonUnique)] // [1, 4, 3]