JavaScript: Map the values of an array to an object using a function

JavaScript: Exercise-82 with Solution

Map Array Values to Object

Write a JavaScript program to map array values to an object using a function. The key-value pairs consist of the original value as the key and the mapped value.

Note: Use an anonymous inner function scope to declare an undefined memory space, using closures to store a return value. Use a new Array to store the array with a map of the function over its data set and a comma operator to return a second step, without needing to move from one context to another (due to closures and order of operations).

• Use Array.prototype.reduce() to apply fn to each element in arr and combine the results into an object.
• Use el as the key for each property and the result of fn as the value.

Sample Solution:

JavaScript Code:

//#Source https://bit.ly/2neWfJ2
// Define the function 'mapObject' to map an array to an object using a given function.
const mapObject = (arr, fn) =>
  // Immediately invoked function expression (IIFE) to avoid creating unnecessary variable assignments.
  (a => (
    // Create an array where the first element is the original array and the second element is the result of applying the function to each element.
    (a = [arr, arr.map(fn)]),
    // Reduce the original array, mapping each element to its corresponding transformed value and constructing a new object.
    a[0].reduce((acc, val, ind) => ((acc[val] = a[1][ind]), acc), {})
  ))();

// Define a function 'squareIt' that squares each element of an array and returns the result as an object.
const squareIt = arr => mapObject(arr, a => a * a);

// Example usage:
console.log(squareIt([1, 2, 3])); // Outputs: { '1': 1, '2': 4, '3': 9 }

Output:

{"1":1,"2":4,"3":9}

Visual Presentation:

Flowchart:

Live Demo:

See the Pen javascript-basic-exercise-82-1 by w3resource (@w3resource) on CodePen.

For more Practice: Solve these Related Problems:

• Write a JavaScript program that converts an array into an object by mapping each value to a key using a provided function.
• Write a JavaScript function that transforms an array of values into an object where keys are the original values and values are generated by a mapping function.
• Write a JavaScript program that iterates over an array and creates an object whose properties are derived from the array elements.

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