In JavaScript, for...in loop is similar to for loop to iterate over an objects or array elements. The loop allows you to perform an action on each property of an object or element of an array.
Syntax of the Javascript For In Loop
for(var property in object)
{
// code to be executed
}
Here, property is a string variable representing the property key, and object is the object to be iterated over.
Iterating Over an Object Example
const numbers = {
"one": 1,
"two": 2,
"three": 3,
"four": 4,
"five": 5
}
for (let num in numbers) {
console.log(`${num}: ${numbers[num]}`);
}
Output:
one: 1
two: 2
three: 3
four: 4
five: 5
Iterating Over an Array Example
const numbers = [1, 2, 3, 4, 5];
for (let index in numbers) {
console.log(`Index: ${index} Value: ${numbers[index]}`);
}
Output:
Index: 0 Value: 1
Index: 1 Value: 2
Index: 2 Value: 3
Index: 3 Value: 4
Index: 4 Value: 5
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