String.prototype.slice()

Try it

const str = "The quick brown fox jumps over the lazy dog.";

console.log(str.slice(31));
// Expected output: "the lazy dog."

console.log(str.slice(4, 19));
// Expected output: "quick brown fox"

console.log(str.slice(-4));
// Expected output: "dog."

console.log(str.slice(-9, -5));
// Expected output: "lazy"

Syntax

slice(indexStart)
slice(indexStart, indexEnd)

Parameters

indexStart

The index of the first character to include in the returned substring.

indexEnd Optional

The index of the first character to exclude from the returned substring.

Return value

A new string containing the extracted section of the string.

Description

slice() extracts the text from one string and returns a new string.

slice() extracts up to but not including indexEnd. For example, str.slice(4, 8) extracts the fifth character through the eighth character (characters indexed 4, 5, 6, and 7):

              indexStart        indexEnd
                                 
| 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |
| T | h | e |   | m | i | r | r | o | r |

                  m   i   r   r
                 _______________
                      
                    Result

• If indexStart >= str.length, an empty string is returned.
• If indexStart < 0, the index is counted from the end of the string. More formally, in this case, the substring starts at max(indexStart + str.length, 0).
• If indexStart is omitted, undefined, or cannot be converted to a number, it's treated as 0.
• If indexEnd is omitted or undefined, or if indexEnd >= str.length, slice() extracts to the end of the string.
• If indexEnd < 0, the index is counted from the end of the string. More formally, in this case, the substring ends at max(indexEnd + str.length, 0).
• If indexEnd <= indexStart after normalizing negative values (i.e., indexEnd represents a character that's before indexStart), an empty string is returned.

Examples

Using slice() to create a new string

The following example uses slice() to create a new string.

const str1 = "The morning is upon us."; // The length of str1 is 23.
const str2 = str1.slice(1, 8);
const str3 = str1.slice(4, -2);
const str4 = str1.slice(12);
const str5 = str1.slice(30);
console.log(str2); // he morn
console.log(str3); // morning is upon u
console.log(str4); // is upon us.
console.log(str5); // ""

Using slice() with negative indexes

The following example uses slice() with negative indexes.

const str = "The morning is upon us.";
str.slice(-3); // 'us.'
str.slice(-3, -1); // 'us'
str.slice(0, -1); // 'The morning is upon us'
str.slice(4, -1); // 'morning is upon us'

This example counts backwards from the end of the string by 11 to find the start index and forwards from the start of the string by 16 to find the end index.

console.log(str.slice(-11, 16)); // "is u"

Here it counts forwards from the start by 11 to find the start index and backwards from the end by 7 to find the end index.

console.log(str.slice(11, -7)); // " is u"

These arguments count backwards from the end by 5 to find the start index and backwards from the end by 1 to find the end index.

console.log(str.slice(-5, -1)); // "n us"

Specifications

Browser compatibility

See also

• String.prototype.substr()
• String.prototype.substring()
• Array.prototype.slice()