Flatten an array - frontend/Javascript Interview Question

This video describes the questions that is repetitively asked in frontend interviews i.e. flatten a deep nested array and follows up that are asked after coding the solution.

Do let me know if you want me to cover some specific topics on frontend interview questions.

[harshitsharma]

thank you, your teaching way is very simple and easy anyone can understand, i saw 4-5 videos regarding this question but didn't get, finally i saw this video and understand very easily, thank you again, you are doing very good

[nixonnelson]

You should put more content regarding these kinda tricky interview questions .

[srinathyadav]

easiest approach is

const ar=[1, 2, 3, 4, 5, [6, [7, 9, 8]]]


function flatten(ar, result=[]){
for(let i=0;i<ar.length;i++){
let value=ar[i];
if(Array.isArray(value)){
flatten(value, result);
}
else{
result.push(value);
}}
return result
}
console.log(flatten(ar));

[kendallsflying]

Thank you for helping with this. It really helps a novice programmer with using recursion.

[murcielago_software]

Fire solution and great vocalization of what you're doing. Thank you! <3

[BulletSP]

had exactly same solution as you but stuck at 🚩 acc = acc.concat(flatten(item)) ... thanks a lot, that's what exactly I needed

[ankita_]

Such a short simple and beginner friendly video. Thank you so much and you just got a new subscriber 😊

[jitujahagirdar]

Wow it was so good to explain. Thanks for this video..!

[ErJokerLover]

Those videos are much helpful for us please make another 😔

[mrtaransraa]

Thanks for the video ☺️ and the great explanation

[mitkopetrov]

If values are only string, number or arrays you can just make the array string and split it by comma. arr = String(arr).split(', ')

[lyessaadoudi]

thank you very much for solution but you can use only function reduce and add methode of : john(" " ) like this :
let flatten = myArray.reduce((acc, item) =>Array.isArray(item) ? acc.concat(item.join("")) : `${acc}${item}`, []);
console.log(flatten);

[High_School_Developer]

const _ = require('lodash') // firstly install npm i lodash
const array = [1, 2, 3, [4, 5, [47, 48, 49], 6], 7, 8, [9, 10, 11]];
const newArray = _.flattenDeep(array)
console.log(newArray);

[krishnachaitanya]

thanks for the video, even i missed the concat one and lost the interview :/

[rahulbhankar]

You can use Array.flat method simply!!

[mohd]

The same question is asked by some interviewer. I missed this video 😟😟😟

[puneetpant]

Recursive Approach :
const array = [1, 2, 3, [4, 5, [47, 48, 49], 6], 7, 8, [9, 10, 11]];

function flatten(array){
function convert(arr){
arr.forEach((key, idx) => {
console.log(arr[idx]);
if(!Array.isArray(arr[idx])){
ans.push(arr[idx]);
}
else{
convert(arr[idx]);
}
})
}
let arr = [...array];
let ans = [];
convert(arr);
return ans;
}

let finalAns = flatten(array);
console.log(finalAns);

[stevenedwards]

I'm getting an "acc is not iterable" error while typing out your exact code and trying to test it.

[High_School_Developer]

I define by a nodejs
npm init
npm install
then dev i lodash

[dylan]

As expected there are 100 different ways to do things with JS (and coding in general). For simplicity however I think this video would've been better if explained using Mozilla's straight forward example:

const array = [1, 2, 3, [4, 5, 6], 7, 8, [9, 10, 11]];
console.log(array.reduce((acc, val) => acc.concat(val), []));