How Can I Iterate Over an Array in JavaScript?

Loop (for each) over an Array in JavaScript

An array in JavaScript is an ordered collection of values, and you can iterate over them using various methods. Here are the key approaches:

Specific to Genuine Arrays

1. For-of Loop (ES2015 )

This method uses implicit iterators and is ideal for simple, asynchronous operations:

const a = ["a", "b", "c"];
for (const element of a) {
    console.log(element);
}
// Output:
// a
// b
// c

2. ForEach and Related (ES5 )

This method calls a callback function for each element in the array:

a.forEach(element => {
    console.log(element);
});
// Output:
// a
// b
// c

3. Simple For Loop

This traditional method provides direct access to the element and its index:

for (let index = 0; index < a.length; ++index) {
    const element = a[index];
    console.log(element);
}
// Output:
// a
// b
// c

4. For-in (Use with Caution)

For-in should be used with safeguards to avoid potential issues with inherited properties:

for (const propertyName in a) {
    if (a.hasOwnProperty(propertyName)) {
        const element = a[propertyName];
        console.log(element);
    }
}
// Output:
// a
// b
// c

Generalizing to Array-Like Objects

In addition to genuine arrays, the approaches can be applied to array-like objects like arguments, iterable objects (ES2015 ), DOM collections, and so on. Keep in mind the following considerations:

• Arguments Object: Use a for-of loop or an explicit iterator, as for-each and for loops won't work correctly.
• Iterable Objects: Use a for-of loop or explicit iterator.
• DOM Collections: Use a for-of loop or explicit iterator.

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