Write a function that takes an array by calling another function to return a value and store it on a new array

Question

I'm having trouble with my code for this javascript exercise as follows:

/**

In the function, accept an array, and call the callback on each element of the array
the callback will return a value - use this value and store it in a new array
for each iteration, the value returned from the callback, should replace the value in the previous array
you should return the new array with the new value
example:
const numbers = [1,2,3,4,5];
const newNumbers = map(numbers, (number) => {
return number + 3;
});
console.log(newNumbers); // [4,5,6,7,8];
@param {number[]} array
@param {Function} callback */

//my javascript code//

function map(array, callback) {
  for (let newArray of array) {
    value(callback(newArray));
  }
  return value;
}
export default map;

What is the use of generating a new array (step 2) and changing the original one (step 3)? — JavaScript
– JavaScript, Commented Oct 20, 2021 at 11:09

Ferin Patel · Accepted Answer · 2021-10-20 11:09:52Z

2

You can simply push callback return into array and return that same array from your custom fucntion.

You can also modify original array using index.

const customMap = (arr, callback) => {
  const finalArr = []
  arr.forEach((item, index) => {
    const res = callback(item)
    finalArr.push(res)
    arr[index] = res // This will modify original array
  })

  return finalArr
}


const numbers = [1, 2, 3, 4, 5];

const newNumbers = customMap(numbers, (number) => {
  return number + 3;
});

console.log(newNumbers);
console.log(numbers);

answered Oct 20, 2021 at 11:09

Ferin Patel

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