In this article, we will learn how to iterate over a JavaScript object. During iteration, you loop through the object’s properties one by one, and depending on the method you use for iteration, you might have different access to these properties
There are many methods to iterate over an object which are discussed below:
- Using for…in loop
- Using Object.entries() method and map() Method
- Using forEach() method and object.keys() Method
Method 1: Using for…in loop
The properties of the object can be iterated over using a for..in loop. This loop is used to iterate over all non-Symbol iterable properties of an object. Some objects may contain properties that may be inherited from their prototypes. The hasOwnProperty() method can be used to check if the property belongs to the object itself. The value of each key of the object can be found by using the key as the index of the object.
Syntax:
for (let key in exampleObj) {
if (exampleObj.hasOwnProperty(key)) {
value = exampleObj[key];
console.log(key, value);
}
}
Example:
Javascript
function iterateObject() { let exampleObj = { book: "Sherlock Holmes", author: "Arthur Conan Doyle", genre: "Mystery" }; for (let key in exampleObj) { if (exampleObj.hasOwnProperty(key)) { value = exampleObj[key]; console.log(key, value); } }}iterateObject(); |
book Sherlock Holmes author Arthur Conan Doyle genre Mystery
Method 2: Using Object.entries() method and map() Method
The Object.entries() method is used to return an array of the object’s own enumerable string-keyed property pairs. The returned array is used with the map() method to extract the key and value from the pairs. The key and values from the key-value pair can be extracted by accessing the first and second index of the array pair. The first index corresponds to the key and the second index corresponds to the value of the pair.
Syntax:
Object.entries(exampleObj).map(entry => {
let key = entry[0];
let value = entry[1];
console.log(key, value);
});
Example:
Javascript
function iterateObject() { let exampleObj = { book: "Sherlock Holmes", author: "Arthur Conan Doyle", genre: "Mystery" }; Object.entries(exampleObj).map(entry => { let key = entry[0]; let value = entry[1]; console.log(key, value); });}iterateObject(); |
book Sherlock Holmes author Arthur Conan Doyle genre Mystery
Method 3: Using forEach() method and object.keys() Method
Object.keys() returns an array of keys of the object and forEach() is an array method that allows you to iterate over each element in the array.
Example:
Javascript
function iterateObject() { let exampleObj = { book: "Sherlock Holmes", author: "Arthur Conan Doyle", genre: "Mystery" }; Object.keys(exampleObj).forEach(key => { const value = exampleObj[key]; console.log(`${key}: ${value}`); });}iterateObject(); |
book: Sherlock Holmes author: Arthur Conan Doyle genre: Mystery
