JavaScript: Create an object with the same keys as the provided object and values generated by running the provided function for each value

JavaScript fundamental (ES6 Syntax): Exercise-84 with Solution

Generate Object Values by Function

Write a JavaScript program to create an object with the same keys as the provided object. It will also generate values generated by running the provided function for each value.

Maps the values of an object using the provided function, generating a new object with the same keys.

• Use Object.keys() to iterate over the object's keys.
• Use Array.prototype.reduce() to create a new object with the same keys and mapped values using fn.

Sample Solution:

JavaScript Code:

//#Source https://bit.ly/2neWfJ2
// Define the function 'mapValues' to map each value of an object to a new value using a given function.
const mapValues = (obj, fn) =>
  // Reduce the object's keys, apply the function to each value along with its key, and store the resulting values in a new object.
  Object.keys(obj).reduce((acc, k) => {
    acc[k] = fn(obj[k], k, obj);
    return acc;
  }, {});

// Example usage:
const users = {
  fred: { user: 'fred', age: 40 },
  pebbles: { user: 'pebbles', age: 1 }
};
console.log(mapValues(users, u => u.age)); // Outputs: { fred: 40, pebbles: 1 }

Output:

{"fred":40,"pebbles":1}

Flowchart:

Live Demo:

See the Pen javascript-basic-exercise-84-1 by w3resource (@w3resource) on CodePen.

Improve this sample solution and post your code through Disqus

Previous: Write a JavaScript program to create a new string with the results of calling a provided function on every character in the calling string.
Next: Write a JavaScript program to replace all but the last number of characters with the specified mask character.