const arr = [1, 3, 5, 7];
const arr2 = [1, 3, 5, 5, 7];
const arr3 = ['d', 'a', 'b', 'c'];
const arr4 = [1, 30, 2, 100];
const users = [
{ name: 'grace', city: 'Toronto', age: 30 },
{ name: 'monica', city: 'New York', age: 24 },
];
Method | Code Example | Result | Return Type | In Place |
---|---|---|---|---|
keys() | const iterator = arr.keys(); for (const key of iterator) { console.log(key); } |
0 1 2 3 |
Array Iterator | No |
values() | const iterator = arr.values(); for (const value of iterator) { console.log(value); } |
1 3 5 7 |
Array Iterator | No |
push() | console.log(arr.push(9)); console.log(arr); |
5 // new length of the array [1, 3, 5, 7, 9] |
number | No |
pop() | console.log(arr.pop()); console.log(arr); |
7 // last element of the array [1, 3, 5] |
element | No |
shift() | console.log(arr.shift()); console.log(arr); |
1 // removed element [3, 5, 7] |
element | No |
unshift() | console.log(arr.unshift(2, 4)); console.log(arr); |
6 // new length of the array [2, 4, 1, 3, 5, 7] |
number | No |
slice() | console.log(arr.slice(1, 3)); console.log(arr); // remain from index 1 to 2 (last one is not included) |
[3, 5] [ 1, 3, 5, 7 ] |
array | No |
splice() | arr.splice(1, 0, 2); // insert ‘2’ at index 1 console.log(arr); |
[1, 2, 3, 5, 7] | array | Yes |
splice() | arr.splice(3, 1, 4); // replace 1 item at index 3 console.log(arr); |
[1, 3, 5, 4] | array | Yes |
splice() | console.log(arr.splice(1, 2)); // remove 2 items from index 1 console.log(arr); |
[3, 5] // removed items [1, 7] // array as a result |
array | Yes |
join() | console.log(arr.join()); | 1,3,5,7 | string | No |
indexOf() | console.log(arr.indexOf(3)); | 1 | number | No |
lastIndexOf() | console.log(arr2.lastIndexOf(5)); | 3 | number | No |
reduce() | console.log(arr.reduce((pre, curr) => pre + curr)); | 16 | number | No |
find() | console.log(arr.find((num) => num > 3)); | 5 | first one | No |
findIndex() | console.log(arr.findIndex((num) => num > 3)); | 2 | first one | No |
every() | console.log(arr.every((num) => num % 2 === 1)); | TRUE | boolean | No |
every() | console.log(arr.every((num) => num > 10)); | FALSE | boolean | No |
some() | console.log(arr.some((num) => num > 5)); | TRUE | boolean | No |
filter() | console.log(arr.filter((num) => num > 3)); const newUsers = users.filter((user) => user.age > 25); console.log(newUsers); |
[5, 7] [ { name: 'grace', city: 'Toronto', age: 30 } ] |
array | No |
map() | arr.map((item) => item * 2) users.map((user) => console.log(user.name)); |
[2, 6, 10, 14] grace monica |
array | No |
flatMap() | console.log(arr.flatMap((x) => [x, x * 2])); | [1, 2, 3, 6, 5, 10, 7, 14] | array | No |
forEach() | arr.forEach((item) => console.log(item * 2)); | 2 6 10 14 |
each element | No |
includes() | console.log(arr.includes(3)); | TRUE | boolean | No |
isArray() | console.log(Array.isArray([1, 2, 3])); | TRUE | boolean | No |
reverse() | console.log(arr.reverse()); | [7, 5, 3, 1] | array | Yes |
concat() | const newArr = arr.concat(['a', 'b']); console.log(newArr); |
[1, 3, 5, 7, "a", "b"] | array | No |
fill() | console.log(arr.fill('a', 1, 3)); // fill with 'a' from position 1 until position 3 |
[1, "a", "a", 7] | array | No |
flat() | const newArr = [1, 3, 5, 7, [2, 4]]; console.log(newArr.flat()); |
[1, 3, 5, 7, 2, 4] | array | No |
Array.from() | console.log(Array.from([1, 2, 3], (x) => x * 2)); | [2, 4, 6] | array | No |
Array.from() | console.log(Array.from('grace')); | ["g", "r", "a", "c", "e"] | array | No |
sort() | console.log(arr3.sort()); | ["a", "b", "c", "d"] | array | Yes |
sort() | console.log(arr4.sort()); console.log(arr4.sort((a, b) => a - b)); |
[ 1, 100, 2, 30 ] [1, 2, 30, 100] |
array | Yes |