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for-in statement

The for-in construct creates a loop to iterate over an object.

Syntax

for (let variableForKey in object) {
	/*
		The iterated object keys will fall
		into the variableForKey one by one.
	*/
};

Example

Let's iterate over the object keys and display them on the screen:

let obj = {a: 1, b: 2, c: 3};

for (let key in obj) {
	console.log(key); // shows 'a', 'b', 'c'
}

Example

And now we will display the object elements:

let obj = {a: 1, b: 2, c: 3};

for (let key in obj) {
	console.log(obj[key]); // shows 1, 2, 3
}

See also

the lesson from JavaScript tutorial
detailing how to work with the for-in loop
the for-of statement
that creates a loop to iterate over an array
the break statement
that breaks a loop
the continue statement
that moves a loop to next iteration

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