flatten array javascript recursion - Brave Search

Javascript recursive array flattening

stackoverflow.com › questions › 30048388 › javascript-recursive-array-flattening

The problem is how you are passing the processing of array, if the value is an array then you are keep calling it causing an infinite loop

function flatten() {
    var flat = [];
    for (var i = 0; i < arguments.length; i++) {
        if (arguments[i] instanceof Array) {
            flat.push.apply(flat, flatten.apply(this, arguments[i]));
        } else {
            flat.push(arguments[i]);
        }
    }
    return flat;
}

Demo: Fiddle

Here's a more modern version:

function flatten(items) {
  const flat = [];

  items.forEach(item => {
    if (Array.isArray(item)) {
      flat.push(...flatten(item));
    } else {
      flat.push(item);
    }
  });

  return flat;
}

Answer from Arun P Johny on Stack Overflow

stackoverflow.com › questions › 30048388 › javascript-recursive-array-flattening

Javascript recursive array flattening - Stack Overflow

The problem is how you are passing the processing of array, if the value is an array then you are keep calling it causing an infinite loop

function flatten() {
    var flat = [];
    for (var i = 0; i < arguments.length; i++) {
        if (arguments[i] instanceof Array) {
            flat.push.apply(flat, flatten.apply(this, arguments[i]));
        } else {
            flat.push(arguments[i]);
        }
    }
    return flat;
}

Demo: Fiddle

Here's a more modern version:

function flatten(items) {
  const flat = [];

  items.forEach(item => {
    if (Array.isArray(item)) {
      flat.push(...flatten(item));
    } else {
      flat.push(item);
    }
  });

  return flat;
}

The clean way to flatten an Array in 2019 with ES6 is `flat()`

Short Answer:

array.flat(Infinity)

Detailed Answer:

const array = [1, 1, [2, 2], [[3, [4], 3], 2]]

// All layers
array.flat(Infinity) // [1, 1, 2, 2, 3, 4, 3, 2]

// Varying depths
array.flat() // [1, 1, 2, 2, Array(3), 2]

array.flat(2) // [1, 1, 2, 2, 3, Array(1), 3, 2]
array.flat().flat() // [1, 1, 2, 2, 3, Array(1), 3, 2]

array.flat(3) // [1, 1, 2, 2, 3, 4, 3, 2]
array.flat().flat().flat() // [1, 1, 2, 2, 3, 4, 3, 2]

Mozilla Docs

Can I Use - 96% Oct '23

developer.mozilla.org › en-US › docs › Web › JavaScript › Reference › Global_Objects › Array › flat

Array.prototype.flat() - JavaScript - MDN Web Docs

The flat() method of Array instances creates a new array with all sub-array elements concatenated into it recursively up to the specified depth.

Videos

Flatten an Array with Recursion in Javascript - YouTube

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freecodecamp.org › news › flatten-array-recursion

How to Flatten an Array in JavaScript Using Recursion

August 18, 2022 - If you carefully observe the above code, line 6 print1ToNo(currentValue + 1) is calling the same function with a new value (whatever the currentValue was, plus 1, i.e currentValue + 1). And it keeps doing it, until the currentValue goes past N, because that's when we told it to return. Now, this is what recursion means. Now, let's get back to our main problem – we need to flatten an Array.

Ashish Maurya's Blog

blog.theashishmaurya.me › flatting-an-object-and-array-using-recursion-and-other-methods

Flatting An object and Array Using Recursion and other Methods

September 27, 2022 - Use recursion to flat a nested object by looping over each property and checking if the typeof the property is of type object, then recursively loop over that object and keep adding the result to the result object.

akhtarvahid.medium.com › flatten-nested-array-recursively-array-flat-in-javascript-5350f9d6f08d

Flatten nested array recursively | Array.flat() in JavaScript | by Vahid Akhtar | Medium

June 30, 2023 - The flat() method creates a new array with all sub-array elements concatenated into it recursively up to the specified depth. ... const hearts = ["💜",["💙"],["❤️‍🩹"]]; const flattened = heart.flat(); console.log(flattened); // ...

gist.github.com › ed1b416d4927388915e5

How to recursively flatten a nested array. · GitHub

Goal was to do this avoiding native Array.prototype.concat method...

github.com › bradtraversy › traversy-js-challenges › blob › main › 04-recursion › 09-flatten-array › readme.md

traversy-js-challenges/04-recursion/09-flatten-array/readme.md at main · bradtraversy/traversy-js-challenges

As the loop iterates through each element of the input array arr, the recursion eventually reaches the point where there are no more elements left to process. When the input array arr is empty, the loop will not execute, and the function will ...

Author bradtraversy

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medium.com › @me.sonu300 › flatten-array-using-recursion-functions-in-javascript-e033e5114e21

Flatten array using recursion functions in JavaScript? | by Sonu Kumar | Medium

June 2, 2024 - //flatten below given array let arr = [1,44, [2, [3,9], 67], 9]; //using recurssion function recur(a) { let newArr = []; for (let i =0 ; i < a.length; i++) { const element = a[i]; if (Array.isArray(element)) { newArr.push(...recur(element)) } else { newArr.push(element) } } return newArr; } console.log(recur(arr)) output: [1,44,2,3,9, 67, 9] //we can also write the same code using foreach: function flattenArray(items) { const flat = []; items.forEach(item => { if (Array.isArray(item)) { flat.push(...flatten(item)); } else { flat.push(item); } }); return flat; } console.log(flattenArray(arr)) output: [1,44,2,3,9, 67, 9]

tutorial.eyehunts.com › home › flatten array javascript recursion | example code

Flatten array JavaScript recursion | Example code

March 30, 2023 - For each element, it checks if it is an array using the Array.isArray method. If the element is an array, the function recursively calls itself on that subarray using concat to add the flattened result to the result array.

tutorialspoint.com › array-flattening-using-loops-and-recursion-in-javascript

Array flattening using loops and recursion in JavaScript

October 20, 2020 - ... const arr = [[1, 2, 3], [4, 5, [5, false, 6, [5, 8, null]]], [6]]; const flatten = function(){ let res = []; for(let i = 0; i < this.length; i++){ if(Array.isArray(this[i])){ res.push(...this[i].flatten()); }else{ res.push(this[i]); }; }; return res; }; Array.prototype.flatten = flatten; ...

medium.com › @conboys111 › flattening-arrays-in-javascript-recursion-vs-iterative-approaches-7164c2b5d165

Flattening Arrays in JavaScript: Recursion vs Iterative Approaches | by myHotTake | Medium

January 2, 2025 - function recursiveFlatten(arr) { return arr.reduce((flat, item) => { return flat.concat(Array.isArray(item) ? recursiveFlatten(item) : item); }, []); } console.log(recursiveFlatten(nested)); // Output: [1, 2, 3, 4, 5, 6] It works, but the problem is deep nesting. With arrays that are too deeply nested (think thousands of levels), the JavaScript call stack would overflow, leading to an error.

4geeks.com › how-to › javascript-array-flatten

How to flatten an array in JavaScript?

July 16, 2025 - If the item is an array we concatenate the variable result with the result of the recursive call of the flattenArray function and if it's not an array we simply push it into the array result.

mccarthydanielle.medium.com › what-happens-when-you-flatten-an-array-using-recursion-da2954deece9

What happens when you flatten an array using recursion. | by Danielle McCarthy | Medium

December 17, 2018 - The result of this recursive call will eventually be pushed to our first function call’s result array. ... This is what the current call stack looks like. Current call stack. This is what the second function call looks like. ... Again, let’s think of this as an entirely new function call. We are invoking flattenArray with [‘ho’]. We know that this is the second element of our original array but for now let’s just focus on this function call.

dtang.dev › 2019-04-05-learning-recursion-in-javascript-part-3

Learning Recursion in JavaScript Part 3 - Flattening Arrays | David Tang

April 5, 2019 - If those values are equal, we stop the recursion. Otherwise, we keep going. If a depth argument isn't passed into flat(), depth will be undefined. Thus, currentDepth, which starts off at 0, will never equal undefined, and our function will flatten the array for however deep it is.

labex.io › tutorials › javascript-flattening-arrays-with-javascript-recursion-28311

Flatten Arrays in JavaScript | Recursion, Reduce, Concat | LabEx

Use the flatten function with two arguments: arr (the array to be flattened) and depth (the maximum number of nested levels to be flattened). Inside the flatten function, use recursion to decrement depth by 1 for each level of depth.

frontendgeek.com › blogs › flatten-nested-array-in-javascript-using-recursion

Flatten Nested Array in JavaScript using Recursion

November 11, 2025 - In the flattenArray function, we iterate over each element of the input array and handle 2 cases · If an element is an array, we recursively call flattenArray on that element and spread its contents into the flatArray.

leetcode.com › problems › flatten-deeply-nested-array › solutions › 3406577 › javascript-a-simple-recursive-solution

[JavaScript] A simple recursive solution - Flatten Deeply ...

April 11, 2023 - Flatten Deeply Nested Array - Given a multi-dimensional array arr and a depth n, return a flattened version of that array. A multi-dimensional array is a recursive data structure that contains integers or other multi-dimensional arrays.

JavaScript in Plain English

javascript.plainenglish.io › 7-ways-to-flatten-arrays-in-javascript-2574db3aff2

7 Ways to Flatten Arrays in JavaScript | by Zachary | JavaScript in Plain English

March 23, 2022 - Loop the original array, determine if the current item is an array, call flatten recursively, and use concat to concatenate the recursive results.

geeksforgeeks.org › implement-custom-array-flat-method-in-javascript

Implement Custom Array Flat method in JavaScript | GeeksforGeeks

April 1, 2024 - By using that function we can directly convert any type of array into 1D array. These are the following approaches to implementing a custom array flat method in JavaScript: ... This approach uses a recursive function to flatten the nested arrays.

helloacm.com › home › javascript › how to unroll/flatten array recursively using javascript?

How to Unroll/Flatten Array Recursively using Javascript? | Algorithms, Blockchain and Cloud

November 26, 2018 - // https://helloacm.com/how-to-unrollflatten-array-recursively-using-javascript/ function unrollArray(x) { let result = []; let func = function(arr) { if (Array.isArray(arr)) { let len = arr.length; for (let i = 0; i < arr.length; ++ i) { func(arr[i]); // do this recursively } } else { result.push(arr); // put the single element to result } } func(x); return result; }