Implement/polyfills Array Functions like a map, reduce, filter, forEach and find in Javascript

This covers polyfills/own implementation of the popular Array Functions like Map, Find, filter, Reduce, ForEach in Javascript. This is very popular among the interviewer in UI technologies.
This is the first video of the JS interview series. Many more such videos will follow. Please suggest any topic which you find difficult, I will try to explain it through the video tutorial.

00:00 introduction
00:25 Polyfill of forEach
10:20 Polyfill of map
16:45 Polyfill of filter
24:04 Polyfill of find
28:35 Polyfill of reduce

[praffulpatil]

The most underrated video for pollyfills… the best explanation i can. Find

[dancelifevarsha]

Very nice explanation.. .. I understood all these concepts so well .. Thank you

[hercules]

Your explanation made this concept so easy in my eyes. Thank you brother! Hope you make more content! :)

[adityamohan]

Thanks for sharing in-depth knowledge on JavaScript ... Glad I learned some new stuff ... Please, upload many videos ... Thank you brother.

[sidd]

Great content, thanks for making it.

[richardjamesbunker]

Thank you for creating this video - I finally understand how these methods work and they don't feel like magic anymore - especially

[warunsharma]

Thanks for sharing this. It helped me.

[rohitgupta]

Just one suggestion for reducer polyfill. Change line 72 to let accumulator = initialValue ? initialValue : this[0] . If there is no initial value reducer function sets the initial value to first element in the array. Amazing explanation otherwise 👍

[jagmeetsingh]

This is super helpful :) Thanks a lot for sharing this..

[jitinbisht]

Great Video 👍 Will follow this channel for all JS topics. Looking forward for more videos. 🍺

[tone_deff]

This is really good!! Subscribed. Looking forward to more videos.

[mayurithakur]

Great Explanation !! Looking forward for more videos 😁

[deepakraghav]

You made polyfills look easy bro !!

Thanks a lot.

[tentx]

thanks a lot bro. u are doing an awesome job by sharing very expensive knowledge

[jitinlamba]

The reduce polyfill will fail, if no initial value is given.
Correct solution:
Array.prototype.myReduce = function (callback, initial) {
let ans = initial ? initial : this[0];
for (let index = initial ? 0 : 1; index < this.length; index++) {
ans = callback(ans, this[index], index, this)
}
return ans;
}

[sharadpawar]

// Simplest way for map

for(let val of this){
callback(val)
}
}

// Simplest way for forEach Method

for(let val of this){
callback(val)
}
}

[samarkhan]

u never use ur mymap function.did u realize?u instead used 'map' while calling(that js provides)