Array Methods

Basic Methods

1. 


2. push(item) Adds an item to the end of the array.

   javascript
   
   
   
   let arr = [1, 2];
   arr.push(3); // [1, 2, 3]
   

3. 


4. pop() Removes and returns the last item in the array.

   javascript
   
   
   
   let arr = [1, 2, 3];
   let last = arr.pop(); // arr: [1, 2], last: 3
   

5. 


6. unshift(item) Adds an item to the beginning of the array.

   javascript
   
   
   
   let arr = [2, 3];
   arr.unshift(1); // [1, 2, 3]
   

7. 


8. shift() Removes and returns the first item in the array.

   javascript
   
   
   
   let arr = [1, 2, 3];
   let first = arr.shift(); // arr: [2, 3], first: 1
   

9. 


10. length Returns the number of elements in the array.

    javascript
    
    
    
    let arr = [1, 2, 3];
    console.log(arr.length); // 3
    

Iteration Methods

6. 


7. forEach(callback) Executes a provided function once for each array element.

   javascript
   
   
   
   let arr = [1, 2, 3];
   arr.forEach(x => console.log(x)); // Logs 1, 2, 3
   

8. map(callback) Creates a new array with the results of calling a function on every element.

   javascript
   
   
   
   let arr = [1, 2, 3];
   let doubled = arr.map(x => x * 2); // [2, 4, 6]
   

9. 


10. filter(callback) Creates a new array with all elements that pass a condition.

    javascript
    
    
    
    let arr = [1, 2, 3, 4];
    let evens = arr.filter(x => x % 2 === 0); // [2, 4]
    

11. 


12. reduce(callback, initialValue) Reduces the array to a single value.

    javascript
    
    
    
    let arr = [1, 2, 3, 4];
    let sum = arr.reduce((acc, curr) => acc + curr, 0); // 1
    

13. 


14. reduceRight(callback, initialValue) Same as reduce but iterates from right to left.

    javascript
    
    
    
    let arr = [1, 2, 3, 4];
    let sum = arr.reduceRight((acc, curr) => acc + curr, 0); // 10
    

15. 


16. some(callback) Returns true if at least one element satisfies the condition.

    javascript
    
    
    
    let arr = [1, 2, 3];
    let hasEven = arr.some(x => x % 2 === 0); // true
    

17. 


18. every(callback) Returns true if all elements satisfy the condition.

    javascript
    
    
    
    let arr = [2, 4, 6];
    let allEven = arr.every(x => x % 2 === 0); // true
    

Searching and Sorting

13. 


14. find(callback) Returns the first element that satisfies the condition.

    javascript
    
    
    
    let arr = [1, 2, 3, 4];
    let firstEven = arr.find(x => x % 2 === 0); // 2
    

15. 


16. findIndex(callback) Returns the index of the first element that satisfies the condition.

    javascript
    
    
    
    let arr = [1, 2, 3, 4];
    let index = arr.findIndex(x => x % 2 === 0); // 1
    

17. 


18. indexOf(item) Returns the index of the first occurrence of an item.

    javascript
    
    
    
    let arr = [1, 2, 3, 2];
    let index = arr.indexOf(2); // 1
    

19. 


20. lastIndexOf(item) Returns the index of the last occurrence of an item.

    javascript
    
    
    
    let arr = [1, 2, 3, 2];
    let index = arr.lastIndexOf(2); //
    

21. 


22. includes(item) Checks if the array contains a specific item.

    javascript
    
    
    
    let arr = [1, 2, 3];
    let hasThree = arr.includes(3); // true
    

23. 


24. sort(compareFunction) Sorts the elements of the array.

    javascript
    
    
    
    let arr = [3, 1, 2];
    arr.sort(); // [1, 2, 3]
    

25. 


26. reverse() Reverses the order of elements in the array.

    javascript
    
    
    
    let arr = [1, 2, 3];
    arr.reverse(); // [3, 2, 1]
    

Modifying and Combining

20. 


21. concat(array) Merges two or more arrays into a new array.

    javascript
    
    
    
    let arr1 = [1, 2];
    let arr2 = [3, 4];
    let merged = arr1.concat(arr2); // [1, 2, 3, 4]
    

22. 


23. slice(start, end) Extracts a portion of the array into a new array.

    javascript
    
    
    
    let arr = [1, 2, 3, 4];
    let sliced = arr.slice(1, 3); // [2, 3]
    

24. 


25. splice(start, deleteCount, ...items) Adds or removes items from an array.

    javascript
    
    
    
    let arr = [1, 2, 3];
    arr.splice(1, 1, 4, 5); // arr: [1, 4, 5, 3
    

26. 


27. flat(depth) Flattens nested arrays into a single array.

    javascript
    
    
    
    let arr = [1, [2, [3]]];
    let flattened = arr.flat(2); // [1, 2, 3]
    

28. 


29. flatMap(callback) Combines map and flat into a single operation.

    javascript
    
    
    
    let arr = [1, 2];
    let result = arr.flatMap(x => [x, x * 2]); // [1, 2, 2, 4]
    

30. 


31. fill(value, start, end) Fills elements with a static value.

    javascript
    
    
    
    let arr = [1, 2, 3];
    arr.fill(0, 1, 3); // [1, 0, 0]
    

Other Methods

26. 


27. join(separator) Joins all elements into a string.

    javascript
    
    
    
    let arr = [1, 2, 3];
    let str = arr.join('-'); // "1-2-3"
    

28. 


29. toString() Converts the array to a string.

    javascript
    
    
    
    let arr = [1, 2, 3];
    let str = arr.toString(); // "1,2,3"
    

30. 


31. Array.isArray(value) Checks if a value is an array.

    javascript
    
    
    
    let value = [1, 2, 3];
    console.log(Array.isArray(value)); // true