JavaScript: Retrieve the value of a specified property from all elements in an array

JavaScript Array: Exercise-27 with Solution

Retrieve Property Values

Write a JavaScript function to retrieve the value of a given property from all elements in an array.

Sample array: [NaN, 0, 15, false, -22, '',undefined, 47, null]
Expected result: [15, -22, 47]

Sample Solution:

JavaScript Code:

// Array of book objects in the library
var library = [ 
  { author: 'Bill Gates', title: 'The Road Ahead', libraryID: 1254},
  { author: 'Steve Jobs', title: 'Walter Isaacson', libraryID: 4264},
  { author: 'Suzanne Collins', title: 'Mockingjay: The Final Book of The Hunger Games', libraryID: 3245}
];

// Function to extract values of a specified property from objects in an array
function property_value(array, property_key) {
  // Initialize an empty array 'arr'
  var arr = [],
    // Initialize index to -1, arrlen to the length of the array (if not provided, default to 0),
    // array_items to store the current array item
    index = -1,
    arrlen = array.length,
    array_items;

  // Iterate through the elements of the array using a while loop
  while (++index < arrlen) {
    // Get the current array item
    array_items = array[index];

    // Check if the array item has the specified property
    if (array_items.hasOwnProperty(property_key)) {
      // If the property exists, add its value to the 'arr' array
      arr[arr.length] = array_items[property_key];
    }
  }

  // Return the 'arr' array containing values of the specified property
  return arr;
}

// Output the result of the property_value function with the 'title' property
console.log(property_value(library, 'title'));

// Output the result of the property_value function with the 'author' property
console.log(property_value(library, 'author'));

Output:

["The Road Ahead","Walter Isaacson","Mockingjay: The Final Book of The Hunger Games"]
["Bill Gates","Steve Jobs","Suzanne Collins"]

Flowchart:

ES6 Version:

// Array of book objects in the library
const library = [ 
  { author: 'Bill Gates', title: 'The Road Ahead', libraryID: 1254},
  { author: 'Steve Jobs', title: 'Walter Isaacson', libraryID: 4264},
  { author: 'Suzanne Collins', title: 'Mockingjay: The Final Book of The Hunger Games', libraryID: 3245}
];

// Function to extract values of a specified property from objects in an array
const property_value = (array, property_key) => {
  // Initialize an empty array 'arr'
  const arr = [];
  // Iterate through the elements of the array using a for...of loop
  for (const array_items of array) {
    // Check if the array item has the specified property
    if (array_items.hasOwnProperty(property_key)) {
      // If the property exists, add its value to the 'arr' array
      arr.push(array_items[property_key]);
    }
  }
  // Return the 'arr' array containing values of the specified property
  return arr;
};

// Output the result of the property_value function with the 'title' property
console.log(property_value(library, 'title'));

// Output the result of the property_value function with the 'author' property
console.log(property_value(library, 'author'));

Live Demo:

See the Pen JavaScript - Retrieve the value of a specified property from all elements in an array - array-ex- 27 by w3resource (@w3resource) on CodePen.

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