How to Iterate Over Object Properties in JavaScript

Iterating over an object’s properties is a common task in JavaScript. However, you can’t simply use methods like map(), forEach(), or a for..of loop to iterate over an object. Attempting to do so will result in errors.

For example, if you have an object called items with properties like 'first', 'second', and 'third', using map() on items will throw a TypeError: items.map is not a function. Similarly, using forEach() or a for..of loop will produce similar errors.

So, how can you effectively iterate over an object’s properties?

One way is to use the for..in loop, which provides a simpler way to iterate:

for (const item in items) {
    console.log(item);
}

Another approach is to use the Object.entries() method to generate an array containing all the enumerable properties of the object. You can then loop through this array using any of the above-mentioned methods:

Object.entries(items).map(item => {
    console.log(item);
});

Object.entries(items).forEach(item => {
    console.log(item);
});

for (const item of Object.entries(items)) {
    console.log(item);
}

By employing these methods, you can effectively iterate over an object’s properties in JavaScript.