Skip to content

Latest commit

 

History

History
120 lines (85 loc) · 3.54 KB

Arrays.md

File metadata and controls

120 lines (85 loc) · 3.54 KB

Arrays In JavaScript

  • In JavaScript, an array is a data structure used to store a collection of elements, which can be of any type such as numbers, strings, or objects.

  • Arrays are useful for grouping similar items together and accessing them through a single variable.

  • To create an array in JavaScript, you can use the array literal notation [], like this:

    let myArray = [];

  • You can also create an array with pre-defined elements by placing them inside the array literal, like this:

    let myArray = [1, 2, 3, "four", true];

  • You can access an element in an array by using its index, which is a zero-based integer representing the position of the element in the array. For example, to access the second element in an array, you would use the index 1, like this:

    let myArray = [1, 2, 3];
console.log(myArray[1]); // outputs 2

  • You can also modify elements in an array by assigning a new value to its index, like this:

    let myArray = [1, 2, 3];
myArray[1] = 4;
console.log(myArray); // outputs [1, 4, 3]

  • You can add new elements to the end of an array using the push() method, like this:

    let myArray = [1, 2, 3];
myArray.push(4);
console.log(myArray); // outputs [1, 2, 3, 4]

  • You can remove the last element of an array using the pop() method, like this:

    let myArray = [1, 2, 3];
myArray.pop();
console.log(myArray); // outputs [1, 2]

  • You can get the length of an array using the length property, like this:

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

Four Different Methods Of Arrays In Javascript

1. shift()

  • The shift() method removes the first element of an array and returns it.
  • This method also changes the length of the array.

Here's an example:

let myArray = ["apple", "banana", "cherry"];
let removedItem = myArray.shift();
console.log(myArray); // outputs ["banana", "cherry"]
console.log(removedItem); // outputs "apple"

2. unshift()

  • The unshift() method adds one or more elements to the beginning of an array and returns the new length of the array.

Here's an example:

let myArray = ["apple", "banana", "cherry"];
let newLength = myArray.unshift("orange", "peach");
console.log(myArray); // outputs ["orange", "peach", "apple", "banana", "cherry"]
console.log(newLength); // outputs 5

3. splice()

  • The splice() method can be used to add or remove elements from an array.
  • It takes three arguments: the index at which to start changing the array, the number of elements to remove, and (optionally) the elements to add.

Here's an example:

Removing elements:

let myArray = ["apple", "banana", "cherry", "date"];
let removedItems = myArray.splice(1, 2);
console.log(myArray); // outputs ["apple", "date"]
console.log(removedItems); // outputs ["banana", "cherry"]

Adding elements:

let myArray = ["apple", "banana", "cherry", "date"];
myArray.splice(1, 2, "orange", "peach");
console.log(myArray); // outputs ["apple", "orange", "peach", "date"]

4. slice()

  • The slice() method creates a new array from a portion of an existing array.
  • It takes two arguments: the index at which to start extracting elements (inclusive) and the index at which to stop (exclusive).

Here's an example:

let myArray = ["apple", "banana", "cherry", "date"];
let newArray = myArray.slice(1, 3);
console.log(newArray); // outputs ["banana", "cherry"]