nitish24p / js-vault Goto Github PK

This page design is completely an open choice.. As long as it fits the theme of the site

Implement a class / function / utility which exhibits an event dispatcher mechanism and the following methods are available

/**
 * Implement an Event dispatcher
 * which has a way to add listener, remove listeners
 * and dispatch events
 *
 *
 * EventDispatcher.addEventListener()
 * EventDispatcher.removeEventListener()
 * EventDispatcher.dispatch(Event)
 *
 */

In array.map impl, why is there a element exists in the array check? What is that supposed to do?
Its literally taking that value out of the array in the previous line and checking if that exists in that line.

From what i know, the in-built impl doesn't protect against array modification. Is it trying to do that?
Atleast why not just check for undefined (say if length got modified).

I have got nothing against useless checks, but that check alone is bringing down the performance from o(n) to o(n**2).

function pipe() {
  // Implement code here
}

const double = (x) => x * 2;
const square = (x) => x * x;
const cube = (x) => x ** 3;

// const value = pipe(double, cube, square)(2); // output 4096
// console.log(value);

Keep the pipe function as generic as possible..

Given a function as mentioned below. Write a utility, promisify, where the usage is as explained below

function asyncFunction(a, b, callback) {
  const isError = Math.random() > 0.7;
  setTimeout(() => {
    if (isError) {
      callback(null, new Error("Something went wrong"));
      return;
    }

    callback(a + b, null);
  }, 3000);
}

function promisify(fn) {
  // Implement Code here
}

// Old ussage
asyncFunction(1,2, function(result, err) {
  console.log(result,err)
})


// New Usage
const promisifiedFn = promisify(asyncFunction);
 promisifiedFn(1, 2)
   .then(res => {
     console.log("result", res);
   })
   .catch(console.log);

What are IIFE

https://developer.mozilla.org/en-US/docs/Glossary/IIFE#:~:text=An%20IIFE%20(Immediately%20Invoked%20Function,soon%20as%20it%20is%20defined.&text=It%20is%20a%20design%20pattern,within%20the%20Grouping%20Operator%20()%20.

Shouldn't the below be callback.call(accumulator, this[index], index, this) instead of callback.call(accumulator, accumulator, this[index], index, this)?

The output is not being reflected inside the output model (Editor)