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JS Reference

Html events, html objects, other references, javascript string slice().

Slice the first 5 positions:

From position 3 to the end:

More examples below.

Description

The slice() method extracts a part of a string.

The slice() method returns the extracted part in a new string.

The slice() method does not change the original string.

The start and end parameters specifies the part of the string to extract.

The first position is 0, the second is 1, ...

A negative number selects from the end of the string.

The split() Method

The substr() Method

The substring() Method

Return Value

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More Examples

From position 3 to 8:

Only the first character:

Only the last character:

The whole string:

Related Pages

JavaScript Strings

JavaScript String Methods

JavaScript String Search

Browser Support

slice() is an ECMAScript1 (ES1) feature.

ES1 (JavaScript 1997) is fully supported in all browsers:

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String.prototype.slice()

The slice() method of String values extracts a section of this string and returns it as a new string, without modifying the original string.

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

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. Changes to the text in one string do not affect the other 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 ):

• 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, undefined, or cannot be converted to a number , 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.

Using slice() to create a new string

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

Using slice() with negative indexes

The following example uses slice() with negative indexes.

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.

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.

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.

Specifications

Browser compatibility.

BCD tables only load in the browser with JavaScript enabled. Enable JavaScript to view data.

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

JavaScript Substring Examples - Slice, Substr, and Substring Methods in JS

In daily programming, we often need to work with strings. Fortunately, there are many built-in methods in JavaScript that help us while working with arrays, strings and other data types. We can use these methods for various operations like searching, replacing, concatenating strings, and so on.

Getting a substring from a string is one of the most common operations in JavaScript. In this article, you’re going to learn how to get a substring by using 3 different built-in methods. But first, let me explain briefly what a substring is.

What is a Substring?

A substring is a subset of another string:

Like in the example above, in some cases we need to get one or more substrings from a complete sentence or a paragraph. Now let’s see how to do that in JavaScript in 3 different ways.

You can also watch the video version of the example usages here:

1. The substring( ) Method

Let’s start with the substring( ) method. This method basically gets a part of the original string and returns it as a new string. The substring method expects two parameters:

• startIndex : represents the starting point of the substring
• endIndex : represents the ending point of the substring (optional)

Let’s see the usage in an example. Suppose that we have the example string below:

Now if we set the startIndex as 0 and the endIndex as 10, then we will get the first 10 characters of the original string:

However, if we set only a starting index and no ending index for this example:

Then we get a substring starting from the 6th character until the end of the original string.

Some additional points:

• If startIndex = endIndex, the substring method returns an empty string
• If startIndex and endIndex are both greater than the length of the string, it returns an empty string
• If startIndex > endIndex, then the substring method swaps the arguments and returns a substring, assuming as the endIndex > startIndex

2. The slice( ) Method

The slice( ) method is similar to the substring( ) method and it also returns a substring of the original string. The slice method also expects the same two parameters:

The common points of substring( ) and slice( ) methods:

• If we don’t set an ending index, then we get a substring starting from the given index number until the end of the original string:

• If we set both the startIndex and the endIndex, then we will get the characters between the given index numbers of the original string:

• If startIndex and endIndex are greater than the length of the string, it returns an empty string

Differences of the slice( ) method:

• If startIndex > endIndex, the slice( ) method returns an empty string
• If startIndex is a negative number, then the first character begins from the end of the string (reverse):

Note: We can use the slice( ) method also for JavaScript arrays. You can find here my other article about the slice method to see the usage for arrays.

3. The substr( ) Method

According to the Mozilla documents , the substr( ) method is considered a legacy function and its use should be avoided. But I will still briefly explain what it does because you might see it in older projects.

The substr( ) method also returns a substring of the original string and expects two parameters as:

• length : number of characters to be included (optional)

You can see the difference here: the substr( ) method expects the second parameter as a length instead of an endIndex:

In this example, it basically counts 5 characters starting with the given startIndex and returns them as a substring.

However, if we don’t define the second parameter, it returns up to the end of the original string (like the previous two methods do):

Note: All 3 methods return the substring as a new string and they don’t change the original string.

So these are the 3 different methods to get a substring in JavaScript. There are many other built-in methods in JS which really help us a lot when dealing with various things in programming. If you find this post helpful, please share it on social media.

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The slice() method in JavaScript is used to extract a portion of a string and create a new string without modifying the original string.

Parameters: This method uses two parameters. This method does not change the original string.

• startingIndex: It is the start position and it is required(The first character is 0).
• endingIndex: ( Optional)It is the end position (up to, but not including). The default is string length.

Return Values:

It returns a part or a slice of the given input string.

JavaScript String slice() Method Examples

Example 1: Slicing String

The code slices the string “Geeks for Geeks” into three parts using the slice() method based on specified indices and logs each part separately.

Example 2: Negative start or end index case

The code slices the string “Ram is going to school” into multiple parts using the slice() method with various index combinations and logs each part separately.

We have a complete list of Javascript string methods, to check those please go through this Javascript String Complete reference article.

  Supported Browser:

• Google Chrome
• Edge  

We have a Cheat Sheet on Javascript where we covered all the important topics of Javascript to check those please go through Javascript Cheat Sheet-A Basic guide to JavaScript .

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Slicing a string using Javascript slice

Pooja hariharan.

Last updated on 21 Feb 2024

Introduction

In this article, we look at the Javascript Slice method then we’ll dive into the code and lastly, we shall look at its limitations.

Table of Contents

What is javascript slice.

• Parameters of Javascript Slice

Code and its Explanation

Limitation & caveats of using javascript slice.

The Slice method in javascript is used to extract a particular section of a string without modifying the original string. Also, the extracted section is returned as a new string.

Syntax of Javascript Slice function

Here str is the original string

Parameters required for Javascript Slice

The beginIndex parameter in Javascript Slice is used to indicate the index at which the extraction should begin. Negative Indexes can also be used to indicate the index.

Example: In order to extract “ple” from “Flexiple” the beginIndex should be 5 as the index of “p” is 5.

Note: An empty string would be returned, In case the beginIndex is greater than or equal to the length of the string.

Subsequently, the endindex parameter in Javascript Slice is used to indicate the index at which the extraction would end. And similar to beginindex, negative indexes can also be used, this would come in handy especially when you are dealing with longer strings.

Example: In order to extract “ple” from “Flexiple” the beginIndex should be 5 and the endindex should be 7 as the index of “e” is 7.

Note: The endinIndex parameter is optional, i.e, in case an endinIndex is specified it would end there else the slice function would end at the last index of the given string.

• Ensure the endinindex is always greater than the begininIndex, else an empty string would be returned
• Using negative index can be tricky, a tip is to make it easier is to consider it as (str.length + beginIndex/ endinIndex)

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Slicing Strings in JS: Essential Tips & Tricks

published at January 28, 2024

Discover the ultimate tricks for slicing strings in JavaScript. Unleash your coding potential and become a master of string manipulation. Read now!

Introduction

String manipulation is a common task in JavaScript development. Whether you need to extract a portion of a string, split it into smaller parts, or simply remove certain characters, knowing how to effectively slice strings in JavaScript is a valuable skill. In this article, we will explore some essential tips and tricks for slicing strings in JavaScript, along with best practices and examples for using various techniques.

• Slice Method The slice() method is a powerful tool for extracting a portion of a string. It takes two optional parameters: the starting index and the ending index (non-inclusive). If no parameters are specified, it will return a copy of the entire string.

Here's an example:

In this example, we start at index 7 and end at index 12, which gives us the substring "World" from the original string.

• Substr Method The substr() method is similar to slice() , but it takes the starting index and the length of the substring as arguments. If the length is not specified, it will return the remaining part of the string from the starting index.

In this example, we start at index 7 and specify a length of 5, which gives us the same result as the slice() method.

• Substring Method The substring() method is also used to extract a portion of a string, but it works slightly differently than slice() and substr() . It takes two parameters: the starting index and the ending index (non-inclusive). If the parameters are in the wrong order, the method will automatically swap them.
• Using Negative Indices JavaScript allows you to use negative indices when slicing strings. Negative indices count from the end of the string, with -1 representing the last character.

In this example, we use negative indices to slice the string from the second last character to the last character, giving us the same result as before.

• Split Method The split() method is commonly used to split a string into an array of substrings based on a specified delimiter. It takes a delimiter parameter and returns an array of substrings.

In this example, we split the string at the space character and get an array with two elements.

• Replace Method The replace() method is useful for replacing specific characters or substrings in a string. It takes two parameters: the search value and the replacement value.

In this example, we replace the comma character with a semicolon.

• Removing Whitespace Sometimes, you may need to remove leading, trailing, or all whitespace from a string. JavaScript provides three useful methods for this: trim() , trimStart() (or trimLeft() ), and trimEnd() (or trimRight() ).

In this example, the leading and trailing whitespace characters are removed from the string.

Slicing strings is a fundamental skill in JavaScript development. By mastering the slice() , substr() , and substring() methods, along with techniques like using negative indices and utilizing the split() and replace() methods, you will have a solid foundation for manipulating strings. Remember to choose the appropriate method based on your specific requirements and use cases.

Further Reading

• MDN Web Docs - String.prototype.slice()
• MDN Web Docs - String.prototype.substr()
• MDN Web Docs - String.prototype.substring()
• MDN Web Docs - String.prototype.split()
• MDN Web Docs - String.prototype.replace()
• MDN Web Docs - String.prototype.trim()
• JavaScript String Methods

Now that you have learned some essential tips and tricks for slicing strings in JavaScript, go ahead and apply this knowledge in your coding projects. Happy coding!

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JavaScript String Slice: Understanding Syntax and Practical Applications

Learn JavaScript string slice syntax & its practical uses. Explore how to extract substrings efficiently for varied programming tasks.

The slice() function in JavaScript is utilized to extract parts of a string and create a new string without modifying the original one. Its flexibility lies in its ability to accept parameters that determine the starting and ending points of the extracted substring.

1. Understanding the Syntax of String Slice

1.1 What is String Slice in JavaScript?

In essence, slice() is a method used to extract a section of a string and return it as a new string, without altering the original string.

1.2 Syntax of String Slice

The syntax involves the string itself, along with parameters specifying the starting and ending indices for slicing.

2. Exploring Parameters in String Slice

Parameters in String Slice

Start Index: Defines the starting point for the extraction.

End Index: Specifies the endpoint for the extraction.

Negative Indexing: Allows counting characters from the end of the string.

3. Practical Applications of String Slice

3.1 Extracting Substrings

One practical application is extracting substrings based on specific character positions within a string. For instance, extracting a username from an email address or a specific phrase from a longer sentence.

3.2 Manipulating Strings

String manipulation involves altering or reorganizing the content of strings. slice() aids in modifying strings without changing the original data.

3.3 Data Formatting

Formatting data is another application; slice() can be used to extract portions of a string to format it according to specific requirements.

4. Examples and Code Snippets

Example 1: Extracting Substrings

Consider an email address "[email protected]." Using slice(), one can extract the username before the "@" symbol.

const email = "[email protected]";

const username = email.slice(0, email.indexOf("@"));

Example 2: Manipulating Strings

Let's capitalize the first letter of a string using slice():

let str = "hello";

str = str[0].toUpperCase() + str.slice(1);

Example 3: Data Formatting

Format a date string using slice():

const dateStr = "2023-11-23";

const formattedDate = dateStr.slice(8) + "-" + dateStr.slice(5, 7) + "-" + dateStr.slice(0, 4);

5. Best Practices for Using String Slice

Ensure validity of start and end indices to avoid unexpected results.

Handle negative indices carefully to prevent unexpected behavior.

Consider error handling for cases where indices exceed string length.

JavaScript's slice() function serves as a valuable tool for string manipulation, enabling developers to extract, manipulate, and format strings efficiently. Understanding its syntax and practical applications empowers developers to wield this method effectively within their code.

Frequently Asked Questions (FAQs)

Q1. Is there a difference between slice() and substring() in JavaScript?

A1: Yes, slice() accepts negative indices while substring() does not.

Q2. Can slice() modify the original string in JavaScript?

A2: No, slice() returns a new string without altering the original one.

Q3. What happens if the end index is greater than the string length in slice()?

A3: It extracts characters up to the string's end without raising an error.

Q4. How does negative indexing work in slice()?

A4: Negative indices count from the end of the string backward.

Q5. Are there scenarios where slice() might not be the best choice for string manipulation?

A5: Yes, for more complex string operations, other methods like regular expressions might be more suitable.

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Master JavaScript String slice() Method

slice() with positive indexes

Slice() with negative indexes, omitting the second argument, browser compatibility.

In JavaScript, the slice() method is a powerful tool for manipulating strings. It can extract parts of a string and return the extracted parts in a new string.

The slice() method accepts two arguments: the start position, and the end position (optional). If the end position is omitted, the method slices out the rest of the string.

Positive indexes represent positions at the start of the string. The first character is at position 0 .

Negative indexes represent positions at the end of the string. The last character is at position -1 .

If you omit the second argument, slice() will return the rest of the string.

All modern browsers fully support the slice() method. For a deeper dive into JavaScript strings, check out our Learn JavaScript course . If you're new to web development, we recommend starting with our HTML Fundamentals course and Introduction to Web Development course before moving on to JavaScript. Once you're comfortable with JavaScript, you can take your skills to the next level with our CSS Introduction course .

Here are some additional resources that you may find helpful: Mozilla Developer Network's guide on JavaScript's slice() method , W3School's tutorial on JavaScript String slice() Method , and JavaScript.info's chapter on strings .

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Exercise: String Slicing

Test your knowledge of the slice function.

Sort the rows given below based on their titles. Make sure you exclude the header row.

Hint: the slice method works in the same way on arrays as on strings.

First, we get rid of the first row:

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String Slicing

String slicing allows you to extract a portion of a string.

It takes two parameters: the starting index and the ending index (optional). It returns a new string containing the extracted portion.

Let's perform such operations on the string "computer". It's structure is the following:

Single argument slicing

Positive argument slicing.

In this example str.slice(3) skips the first 3 symbols of the string - c , o and m .

The other part of the string (starting from the 3rd index - p ) is extracted - puter .

Negative argument slicing

Negative indexes track the string characters in reverse.

In this example str.slice(-3) extracts only the last 3 symbols of the string - t , e and r .

Two arguments slicing

Positive arguments slicing.

In this example str.slice(3, 5) skips the first 3 symbols of the string - c , o and m .

Afterwards it takes the rest of the string until it reaches the 5th symbol - u .

Negative arguments slicing

In this example str.slice(-5, -2) starts slicing at 5th symbol counting backwards and ends before the second symbol counting backwards.

Mixed arguments slicing

Both positive and negative arguments can be specified.

In this example str.slice(1, -1) starts after the first symbol and ends before the last symbol.

Invalid cases

An invalid case simply returns an empty string. In such cases the slicing start argument position is after the slicing end.

Example of valid and invalid case:

Another invalid slicing case is specifying starting argument that's beyound the string's bounds:

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