JavaScript Array slice()

 let numbers = [2, 3, 5, 7, 11, 13, 17]; 
// create another array by slicing numbers from index 3 to 5 let newArray = numbers.slice(3, 6);
 console.log(newArray); // Output: [ 7, 11, 13 ]

slice() Syntax

The syntax of the slice() method is:

 arr.slice(start, end)

Here, arr is an array.

slice() Parameters

The slice() method takes in:

• start (optional) - Starting index of the selection. If not provided, the selection starts at start 0.
• end (optional) - Ending index of the selection (exclusive). If not provided, the selection ends at the index of the last element.

slice() Return Value

• Returns a new array containing the extracted elements.

Example 1: JavaScript slice() method

 let languages = ["JavaScript", "Python", "C", "C++", "Java"]; // slicing the array (from start to end) 
let new_arr = languages.slice();
 console.log(new_arr); // [ 'JavaScript', 'Python', 'C', 'C++', 'Java' ] // slicing from the third element 
let new_arr1 = languages.slice(2);
 console.log(new_arr1); // [ 'C', 'C++', 'Java' ] // slicing from the second element to fourth element 
let new_arr2 = languages.slice(1, 4);
 console.log(new_arr2); // [ 'Python', 'C', 'C++' ]

Output

 [ 'JavaScript', 'Python', 'C', 'C++', 'Java' ] [ 'C', 'C++', 'Java' ] [ 'Python', 'C', 'C++' ]

Example 2: JavaScript slice() With Negative index

In JavaScript, you can also use negative start and end indices. The index of the last element is -1, the index of the second last element is -2, and so on.

 const languages = ["JavaScript", "Python", "C", "C++", "Java"]; // slicing the array from start to second-to-last 
let new_arr = languages.slice(0, -1);
 console.log(new_arr); // [ 'JavaScript', 'Python', 'C', 'C++' ] // slicing the array from third-to-last 
let new_arr1 = languages.slice(-3);
 console.log(new_arr1); // [ 'C', 'C++', 'Java' ]

Output

 [ 'JavaScript', 'Python', 'C', 'C++' ] [ 'C', 'C++', 'Java' ]

Example 3: JavaScript slice() with Objects as Array Elements

The slice() method shallow copies the elements of the array in the following way:

• It copies object references to the new array. (For example, a nested array) So if the referenced object is modified, the changes are visible in the returned new array.
• It copies the value of strings and numbers to the new array.

 let human = { name: "David", age: 23, }; let arr = [human, "Nepal", "Manager"]; 
let new_arr = arr.slice();
 // original object console.log(arr[0]); // { name: 'David', age: 23 } // making changes to the object in new array new_arr[0].name = "Levy"; // changes are reflected console.log(arr[0]); // { name: 'Levy', age: 23 }

Output

 { name: 'David', age: 23 } { name: 'Levy', age: 23 }

Also Read:

• JavaScript Array.splice()
• JavaScript String slice()