JavaScript Array Iteration Methods

JavaScript provides powerful array iteration methods to work with elements easily. These methods help us write cleaner and shorter code.

1. forEach()

Executes a function for each element.

let nums = [1, 2, 3];
nums.forEach(n => console.log(n));

Output:

1
2
3

2. map()

Creates a new array by modifying each element.

let nums = [1, 2, 3];
let result = nums.map(n => n * 2);
console.log(result);

Output:

[2, 4, 6]

3. flatMap()

Maps and flattens the array.

let arr = [1, 2];
let result = arr.flatMap(x => [x, x * 2]);
console.log(result);

Output:

[1, 2, 2, 4]

4. filter()

Filters elements based on condition.

let nums = [1, 2, 3, 4];
let even = nums.filter(n => n % 2 === 0);
console.log(even);

Output:

[2, 4]

5. reduce()

Reduces array to a single value.

let nums = [1, 2, 3];
let sum = nums.reduce((acc, val) => acc + val, 0);
console.log(sum);

Output:

6

6. every()

Checks if all elements satisfy condition.

let nums = [2, 4, 6];
let allEven = nums.every(n => n % 2 === 0);
console.log(allEven);

Output:

true

7. some()

Checks if at least one element satisfies condition.

let nums = [1, 3, 4];
let hasEven = nums.some(n => n % 2 === 0);
console.log(hasEven);

Output:

true

8. Array.from()

Creates array from iterable.

let str = "hi";
let arr = Array.from(str);
console.log(arr);

Output:

['h', 'i']

9. keys()

Returns array indices.

let arr = ["a", "b"];
console.log([...arr.keys()]);

Output:

[0, 1]

10. Spread Operator (...)

Expands array elements.

let arr = [1, 2];
let newArr = [...arr, 3, 4];
console.log(newArr);

Output:

[1, 2, 3, 4]

Reference
W3Schools
https://www.w3schools.com/js/js_array_iteration.asp