JavaScript Array Methods Examples: A Comprehensive Guide (Methods)

Complete examples of all major JavaScript array methods.

Categories of Array Methods:

1. Modification Methods (modify original array)

• push(), pop(), shift(), unshift(), reverse(), sort(), splice(), fill()

2. Non-modifying Methods (return new array/value)

• map(), filter(), concat(), slice(), toReversed(), toSorted(), toSpliced()

3. Search Methods

• indexOf(), includes(), find(), findIndex(), findLast(), findLastIndex()

4. Iteration Methods

• forEach(), map(), filter(), reduce(), every(), some()

5. Array Creation Methods

• Array.from(), Array.of(), Array.fromAsync()

6. Other Utility Methods

• join(), flat(), flatMap(), entries(), values(), with()

Examples of all 31 methods below:

1. concat() - Merges two or more arrays

const arr1 = [1, 2];
const arr2 = [3, 4];
console.log(arr1.concat(arr2)); // Output: [1, 2, 3, 4]

2. join() - Creates a string from array elements

const fruits = ['Apple', 'Banana', 'Orange'];
console.log(fruits.join(', ')); // Output: "Apple, Banana, Orange"

3. fill() - Fills array elements with a static value

const numbers = [1, 2, 3, 4];
console.log(numbers.fill(0)); // Output: [0, 0, 0, 0]

4. includes() - Checks if an array contains a specific element

const colors = ['red', 'blue', 'green'];
console.log(colors.includes('blue')); // Output: true

5. indexOf() - Finds the first index of an element

const numbers2 = [1, 2, 3, 2];
console.log(numbers2.indexOf(2)); // Output: 1

6. reverse() - Reverses array elements

const letters = ['a', 'b', 'c'];
console.log(letters.reverse()); // Output: ['c', 'b', 'a']

7. sort() - Sorts array elements

const unsorted = [3, 1, 4, 1, 5];
console.log(unsorted.sort()); // Output: [1, 1, 3, 4, 5]

8. splice() - Adds/removes elements from array

const months = ['Jan', 'March', 'April'];
months.splice(1, 0, 'Feb');
console.log(months); // Output: ['Jan', 'Feb', 'March', 'April']

9. at() - Returns element at specified index

const array1 = [5, 12, 8, 130, 44];
console.log(array1.at(2)); // Output: 8

10. copyWithin() - Copies array elements to another position

const array2 = ['a', 'b', 'c', 'd', 'e'];
console.log(array2.copyWithin(0, 3, 4)); // Output: ['d', 'b', 'c', 'd', 'e']

11. flat() - Creates a new array with sub-array elements concatenated

const arr3 = [1, 2, [3, 4, [5, 6]]];
console.log(arr3.flat(2)); // Output: [1, 2, 3, 4, 5, 6]

12. Array.from() - Creates array from array-like object

console.log(Array.from('hello')); // Output: ['h', 'e', 'l', 'l', 'o']

13. findLastIndex() - Returns last index that satisfies condition

const numbers3 = [5, 12, 8, 130, 44, 8];
console.log(numbers3.findLastIndex(num => num === 8)); // Output: 5

14. forEach() - Executes function for each array element

const numbers4 = [1, 2, 3];
numbers4.forEach(num => console.log(num * 2)); // Output: 2, 4, 6

15. every() - Tests if all elements pass condition

const numbers5 = [1, 2, 3, 4, 5];
console.log(numbers5.every(num => num > 0)); // Output: true

16. entries() - Returns array iterator with key/value pairs

const fruits2 = ['Apple', 'Banana'];
const iterator = fruits2.entries();
console.log([...iterator]); // Output: [[0, 'Apple'], [1, 'Banana']]

17. values() - Returns array iterator with values

const fruits3 = ['Apple', 'Banana'];
const values = [...fruits3.values()];
console.log(values); // Output: ['Apple', 'Banana']

18. toReversed() - Returns new reversed array

const arr4 = [1, 2, 3];
console.log(arr4.toReversed()); // Output: [3, 2, 1]
console.log(arr4); // Original array unchanged: [1, 2, 3]

19. toSorted() - Returns new sorted array

const arr5 = [3, 1, 2];
console.log(arr5.toSorted()); // Output: [1, 2, 3]
console.log(arr5); // Original array unchanged: [3, 1, 2]

20. toSpliced() - Returns new array with splice operation

const arr6 = [1, 2, 3];
console.log(arr6.toSpliced(1, 1, 'two')); // Output: [1, 'two', 3]
console.log(arr6); // Original array unchanged: [1, 2, 3]

21. with() - Returns new array with element replaced

const arr7 = [1, 2, 3];
console.log(arr7.with(1, 'two')); // Output: [1, 'two', 3]
console.log(arr7); // Original array unchanged: [1, 2, 3]

22. Array.fromAsync() - Creates array from async iterable

async function* asyncGenerator() {
  yield 1;
  yield 2;
}
Array.fromAsync(asyncGenerator()).then(array => console.log(array)); // Output: [1, 2]

23. Array.of() - Creates array from arguments

console.log(Array.of(1, 2, 3)); // Output: [1, 2, 3]

24. map() - Creates new array with results of callback

const numbers6 = [1, 2, 3];
console.log(numbers6.map(x => x * 2)); // Output: [2, 4, 6]

25. flatMap() - Maps and flattens result

const arr8 = [1, 2, 3];
console.log(arr8.flatMap(x => [x, x * 2])); // Output: [1, 2, 2, 4, 3, 6]

26. reduce() - Reduces array to single value (left to right)

const numbers7 = [1, 2, 3, 4];
console.log(numbers7.reduce((acc, curr) => acc + curr, 0)); // Output: 10

27. reduceRight() - Reduces array to single value (right to left)

const numbers8 = [1, 2, 3, 4];
console.log(numbers8.reduceRight((acc, curr) => acc + curr, 0)); // Output: 10

28. some() - Tests if at least one element passes condition

const numbers9 = [1, 2, 3, 4, 5];
console.log(numbers9.some(num => num > 4)); // Output: true

29. find() - Returns first element that passes condition

const numbers10 = [5, 12, 8, 130, 44];
console.log(numbers10.find(num => num > 10)); // Output: 12

30. findIndex() - Returns first index that passes condition

const numbers11 = [5, 12, 8, 130, 44];
console.log(numbers11.findIndex(num => num > 10)); // Output: 1

31. findLast() - Returns last element that passes condition

const numbers12 = [5, 12, 8, 130, 44];
console.log(numbers12.findLast(num => num > 10)); // Output: 44

Key points:

• Each method has a specific task, such as sorting, reversing, or finding an element in an array.
• Some methods modify the original array, like sort() and reverse().
• Some methods return a new array, like map() and filter().
• Some modern methods, like toSorted() and toReversed(), keep the original array unchanged and return a new array.

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