Array.flat() method in JavaScript.

The JavaScript Array.flat() method is used to flatten an array recursively up to a specified depth. It doesn’t manipulate the original array but creates a new flattened array.

Following is the code for the Array.flat() method −


 Live Demo

<!DOCTYPE html>
<html lang="en">
<meta charset="UTF-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
   body {
      font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
   .result,.sample {
      font-size: 20px;
      font-weight: 500;
<h1>Array.flat() method</h1>
<div class="sample"><pre>[1,2,3,[4,5],[6,[7,8]]]</pre></div>
<div style="color: green;" class="result">After flat : <br></div>
<button class="Btn">CLICK HERE</button>
Click on the above button to flat the above array by depth 1
   let resEle = document.querySelector(".result");
   let sampleEle = document.querySelector(".sample");
   let arr = [1,2,3,[4,5],[6,[7,8]]];
   document.querySelector(".Btn").addEventListener("click", () => {
      let store = arr.flat(1);
      store.forEach((item,index) => {
         resEle.innerHTML += index + ' : ' + item + ' ';


The above code will produce the following output −

On clicking the ‘CLICK HERE’ button −

Updated on: 16-Jul-2020


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