how to create own map function in typescript

Question

We are creating our own map function. Sometimes in an interview, Interviewer asked for the implementation of the map function. How it behaves internally using a callback.


    Map Polyfill
 
// @ts-ignore
// eslint-disable-next-line no-extend-native
Array.prototype.myOwnMap = function myOwnMap(
  callback: (inputElement: number, index?: number, array?: number[]) => number
): number[] {
  const outputArr: number[] = [];
  for (let iterator = 0; iterator < inputElements.length; iterator++) {
    outputArr.push(callback(inputElements[iterator], iterator, inputElements));
  }
  return outputArr;
};

// @ts-ignore
const outputElements: number[] = inputElements.myOwnMap(
  (element: number, index: number, array: number[]) => {
    return element + index * 2;
  }
);
console.log("We are expecting result is [ 1, 4, 7, 10, 13, 16 ]", outputElements);```

Does this answer your question? Creating my own array.prototype.map method. How can I access the array? — Nikita Skrebets
– Nikita Skrebets, Commented Jan 3, 2022 at 2:42

Ayush mishra · Accepted Answer · 2021-12-24 15:57:05Z

0

In the same way, I created polyfill for filter functions as well.

/**
 *   Filter polyfill
 */

//@ts-ignore
// eslint-disable-next-line no-extend-native
Array.prototype.myOwnFilter = function myOwnFilter(
  callback: (value: number, index?: number, array?: number[]) => number
): number[] {
  const newArrayElements: number[] = [];
  for (let iterator = 0; iterator < inputElements.length; iterator++) {
    if (!!callback(inputElements[iterator], iterator, inputElements))
      newArrayElements.push(inputElements[iterator]);
  }
  return newArrayElements;
};

// @ts-ignore
const outputElement: number[] = inputElements.myOwnFilter(
  (value: number) => value % 2 === 0
);

console.log("We are expecting array [2,4,6]", outputElement);

answered Dec 24, 2021 at 15:57

Ayush mishra

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