Use JavaScript flat() method to create a new Flatten array with all sub-array elements concatenated into it recursively up to the specified depth.
flat()
flat(depth)
A depth level is an option and it specifies how deep a nested array structure should be flattened. Defaults to 1.
If you’re working with an older version of JavaScript, you can use the reduce() method to flatten the array manually.
JavaScript Flatten Array
Simple example code obtaining a flattened array by specifying the depth.
<!DOCTYPE html>
<html>
<body>
<script>
const arr1 = [0, 1, 2, [3, 4]];
console.log(arr1.flat());
const arr2 = [0, 1, 2, [[[3, 4]]]];
console.log(arr2.flat(2));
</script>
</body>
</html>
Output:
Different methods to flatten an array
Using concat() and apply()
let arr = [
[1, 2],
[3, 4],
[5, 6][7, 8, 9],
[10, 11, 12, 13, 14, 15]
];
let flatArray = [].concat.apply([], arr);
//Output: [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 ]Using the spread operator
let flatArray = [].concat(...arr);
//Output: [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 ]Using the reduce method
let flatArray = arr.reduce((acc, curVal) => {
return acc.concat(curVal)
}, []);
//Output: [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 ]Comment if you have any doubts or suggestions on this JS Array topic.
Note: The All JS Examples codes are tested on the Firefox browser and the Chrome browser.
OS: Windows 10
Code: HTML 5 Version