JavaScript: Retrieve a set of properties indicated by the given selectors from an object

JavaScript fundamental (ES6 Syntax): Exercise-49 with Solution

Retrieve Selected Properties from Object

Write a JavaScript program to retrieve a set of properties indicated by the given selectors from an object.

• Use Array.prototype.map() for each selector, String.prototype.replace() to replace square brackets with dots.
• Use String.prototype.split('.') to split each selector.
• Use Array.prototype.filter() to remove empty values and Array.prototype.reduce() to get the value indicated by each selector.

Sample Solution:

JavaScript Code:

//#Source https://bit.ly/2neWfJ2
// Define a function 'get' that retrieves values from an object based on selector strings.
const get = (from, ...selectors) =>
  // Map over the selectors array.
  [...selectors].map(s =>
    // Replace square brackets with dots, split by dots, filter out empty strings,
    // and then recursively retrieve the value from the object.
    s
      .replace(/\[([^\[\]]*)\]/g, '.$1.')
      .split('.')
      .filter(t => t !== '')
      .reduce((prev, cur) => prev && prev[cur], from)
  );

// Define an object 'obj' with nested properties.
const obj = { selector: { to: { val: 'val to select' } }, target: [1, 2, { a: 'test' }] };

// Use the 'get' function to retrieve values from 'obj' based on selectors.
console.log(get(obj, 'selector.to.val', 'target[0]', 'target[2].a')); 
// Output: [ 'val to select', 1, 'test' ]

Output:

["val to select",1,"test"]

Flowchart:

Live Demo:

See the Pen javascript-basic-exercise-1-49 by w3resource (@w3resource) on CodePen.

For more Practice: Solve these Related Problems:

• Write a JavaScript program that returns a new object containing only the specified keys from the original object.
• Write a JavaScript function that uses array filtering to extract selected properties from an object based on a key list.
• Write a JavaScript program that destructures an object to retrieve only the desired properties and reassembles them into a new object.

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