JavaScript Program to Extract Given Property Values from Objects as Array

In this example, you will learn to write a JavaScript program that will extract the value of a property as an array from the array of objects.

To understand this example, you should have the knowledge of the following JavaScript programming topics:


Example 1: Extract Value Using map()

// program to extract value as an array from an array of objects

function extractValue(arr, prop) {

    // extract value from property
    let extractedValue = arr.map(item => item[prop]);

    return extractedValue;

}

const objArray = [{a: 1, b: 2}, {a: 4, b: 5}, {a: 8, b: 9}];

// passing an array of objects and property 'a' to extract
const result = extractValue(objArray, 'a');
console.log(result);

Output

[1, 4, 8]

In the above program, the property's value of key a is extracted from each object of an array.

The map() method is used to iterate through all the elements of an array and extract property values of key a.

Note: You could also use a regular function instead of an arrow function.

let extractedValue = arr.map(function(item) {return item[prop]});

Example 2: Extract Value Using for Loop

// program to extract value as an array from an array of objects

function extractValue(arr, prop) {

    let extractedValue = [];

    for (let i=0; i < arr.length ; ++i) {

        // extract value from property
        extractedValue.push(arr[i][prop]);
    }
    return extractedValue;
}

const objArray = [{a: 1, b: 2}, {a: 4, b: 5}, {a: 8, b: 9}];

// passing an array of objects and property 'a' to extract
const result = extractValue(objArray, 'a');
console.log(result);

Output

[1, 4, 8]

In the above program, the property value of key a is extracted from each object of an array.

  • Initially, the extractedValue array is empty.
  • The for loop is used to iterate through all the elements of an array.
  • During each iteration, the value of property a is pushed to the extractedValue array.