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What is the difference between for…in and for…of variables?

Asked on Jul 17, 2025

Answer

The "for...in" loop iterates over the enumerable properties of an object, while the "for...of" loop iterates over the values of iterable objects like arrays, strings, and more.

// Example of for...in
        const obj = { a: 1, b: 2, c: 3 };
        for (const key in obj) {
            console.log(key); // Outputs: "a", "b", "c"
        }

        // Example of for...of
        const array = [10, 20, 30];
        for (const value of array) {
            console.log(value); // Outputs: 10, 20, 30
        }

Additional Comment:

"for...in" is used for iterating over object properties.
"for...of" is used for iterating over iterable objects like arrays, strings, Maps, Sets, etc.
"for...in" returns keys (property names), while "for...of" returns values.
Use "for...in" when you need to work with object properties, and "for...of" when you need to work with values of an iterable.

✅ Answered with JavaScript best practices.

Ask any question about JavaScript here... and get an instant response.

What is the difference between for…in and for…of variables?

Asked on Jul 17, 2025

Answer

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