Array Properties
| Property | Description |
|---|---|
length |
Sets or returns the number of elements in an array. |
prototype |
Allows you to add new properties and methods to an Array object. |
Array Methods
| Method | Description |
|---|---|
concat() |
Merge two or more arrays, and returns a new array. |
copyWithin() |
Copies part of an array to another location in the same array and returns it. |
entries() |
Returns a key/value pair Array Iteration Object. |
every() |
Checks if every element in an array pass a test in a testing function.
const arr = [1, 2, 3, 4, 5, 6];
// all elements are greater than 4
const greaterFour = arr.every(num => num > 4);
console.log(greaterFour); // output: false
// all elements are less than 10
const lessTen = arr.every(num => num < 10);
console.log(lessTen); // output: true
|
fill() |
Fill the elements in an array with a static value. |
filter() |
This method create new array with only elements passed condition inside the provided function.
const arr = [1, 2, 3, 4, 5, 6];
// item(s) greater than 3
const filtered = arr.filter(num => num > 3);
console.log(filtered); // output: [4, 5, 6]
console.log(arr); // output: [1, 2, 3, 4, 5, 6]
|
find() |
Returns the value of the first element in an array that pass the test in a testing function. |
findIndex() |
Returns the index of the first element in an array that pass the test in a testing function. |
forEach() |
Calls a function once for each array element.
const arr = [1, 2, 3, 4, 5, 6];
arr.forEach(item => {
console.log(item); // output: 1 2 3 4 5 6
});
|
from() |
Creates an array from an object. |
includes() |
This method check if array includes the item passed in the method. const arr = [1, 2, 3, 4, 5, 6];
arr.includes(2); // output: true
arr.includes(7); // output: false
|
indexOf() |
Search the array for an element and returns its first index. |
isArray() |
Determines whether the passed value is an array. |
join() |
Joins all elements of an array into a string. |
keys() |
Returns a Array Iteration Object, containing the keys of the original array. |
lastIndexOf() |
Search the array for an element, starting at the end, and returns its last index. |
map() |
Creates a new array with the results of calling a function for each array element. const arr = [1, 2, 3, 4, 5, 6];
// add one to every element
const oneAdded = arr.map(num => num + 1);
console.log(oneAdded); // output [2, 3, 4, 5, 6, 7]
console.log(arr); // output: [1, 2, 3, 4, 5, 6]
|
pop() |
Removes the last element from an array, and returns that element. |
push() |
Adds one or more elements to the end of an array, and returns the array’s new length. |
reduce() |
Reduce the values of an array to a single value (from left-to-right). const arr = [1, 2, 3, 4, 5, 6];
const sum = arr.reduce((total, value) => total + value, 0);
console.log(sum); // 21
|
reduceRight() |
Reduce the values of an array to a single value (from right-to-left). |
reverse() |
Reverses the order of the elements in an array. |
shift() |
Removes the first element from an array, and returns that element. |
slice() |
Selects a part of an array, and returns the new array. |
some() |
Checks if any of the elements in an array passes the test in a testing function.
const arr = [1, 2, 3, 4, 5, 6];
// at least one element is greater than 4?
const largeNum = arr.some(num => num > 4);
console.log(largeNum); // output: true
// at least one element is less than or equal to 0?
const smallNum = arr.some(num => num <= 0);
console.log(smallNum); // output: false
|
sort() |
Sorts the elements of an array const arr = [1, 2, 3, 4, 5, 6];
const alpha = ['e', 'a', 'c', 'u', 'y'];
// sort in descending order
descOrder = arr.sort((a, b) => a > b ? -1 : 1);
console.log(descOrder); // output: [6, 5, 4, 3, 2, 1]
// sort in ascending order
ascOrder = alpha.sort((a, b) => a > b ? 1 : -1);
console.log(ascOrder); // output: ['a', 'c', 'e', 'u', 'y'] |
splice() |
Adds/Removes elements from an array. |
toString() |
Converts an array to a string, and returns the result. |
unshift() |
Adds new elements to the beginning of an array, and returns the array’s new length. |
values() |
Returns a Array Iteration Object, containing the values of the original array. |
