Write a function `myMap(arr, callback)` that works like Array.prototype.map without using the built-in map method.

Problem Statement

<p>Write a function <code>myMap(arr, callback)</code> that works like Array.prototype.map without using the built-in map method.</p>

Examples

Input: myMap([1, 2, 3], x => x * 2)

Output: [2, 4, 6]

Explanation: Transforms every item through the callback.

Complexity

Time Complexity: O(N)

Space Complexity: O(N)

Hints

💡 Hint 1: Create a new array to store results. 💡 Hint 2: Loop through the array and call the callback with (element, index, array). 💡 Hint 3: Push the callback result into the new array for each element.

Editorial & Approach

Problem Overview & Intuition

To solve Implement Array.map, we consider the execution characteristics of JavaScript engines. Write a function `myMap(arr, callback)` that works like Array.prototype.map without using the built-in map method. By utilizing idiomatic language constructs and clean algorithmic principles, we can accomplish this with optimal time and memory usage.

Step-by-Step Approach

Understand Problem Contract: Identify input arguments, return type expectations, and edge cases (empty inputs, nullish values).
Choose Core Mechanism: Use modern JavaScript patterns (create a new array to store results).
Implement Logic: Handle state and transformations efficiently (loop through the array and call the callback with (element, index, array)).
Return Result: Ensure proper return format and preserve caller context if applicable.

Optimal Implementation (JavaScript)

function myMap(arr, callback) {
  const result = [];
  for (let i = 0; i < arr.length; i++) {
    result.push(callback(arr[i], i, arr));
  }
  return result;
}

Complexity Analysis

Time Complexity O(N) single linear scan through array

Space Complexity O(N) new output array (O(1) for reduce)

Edge Cases & Corner Traps Handled

Empty or boundary inputs (empty arrays, strings, zero length).
Type checks and unexpected values (e.g. null, undefined, negative numbers).
Closure preservation and memory isolation between separate invocations.

Implement Array.map

Medium

Write a function myMap(arr, callback) that works like Array.prototype.map without using the built-in map method.

Example Scenarios

1Example 1

Input: myMap([1, 2, 3], x => x * 2)

Output: [2, 4, 6]

Explanation:

Transforms every item through the callback.

Editor

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Output:Click "Run" above to execute and verify your code here.

[[2,4,6],["a0","b1"]]