Strings

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What are JavaScript Strings?

In JavaScript, a string is a sequence of characters enclosed in single or double quotes. Strings can contain letters, numbers, symbols, and spaces.

Here are some examples of JavaScript strings:

  1. let name = "John Doe";
  2. let message = 'Hello, World!';
  3. let quote = "I'm loving JavaScript!";

In the above examples, `name`, `message`, and `quote` are all JavaScript string variables.

String Manipulation

JavaScript provides numerous methods to manipulate strings. These methods can be used to perform various operations on strings, such as concatenation, extracting substrings, converting case, and more. Let's explore some commonly used string manipulation methods:

Concatenation

Concatenation is the process of combining two or more strings into a single string. In JavaScript, you can use the `+` operator or the `concat()` method to concatenate strings. Here's an example of concatenating two strings:

  1. let firstName = "John";
  2. let lastName = "Doe";
  3. let fullName = firstName + " " + lastName;
  4. console.log(fullName); // Output: John Doe
  5.  
  6. // Using concat() method
  7. let hello = "Hello";
  8. let world = "World";
  9. let greeting = hello.concat(" ", world);
  10. console.log(greeting); // Output: Hello World

In the above examples, `fullName` and `greeting` are new strings created by concatenating existing strings.

String Length

To determine the length of a string, you can use the `length` property. The `length` property returns the number of characters in a string, including spaces and special characters. Here's an example:

  1. let message = "Hello, World!";
  2. console.log(message.length); // Output: 13

In the above example, `message.length` returns the length of the string "Hello, World!", which is 13.

Accessing Characters

You can access individual characters within a string by using square brackets `[ ]` and the index of the character you want to retrieve. In JavaScript, string indexing starts at 0. Here's an example:

  1. let message = "Hello, World!";
  2. console.log(message[0]); // Output: H
  3. console.log(message[7]); // Output: W

In the above example, `message[0]` returns the first character of the string "Hello, World!", which is 'H'. `message[7]` returns the 8th character, which is 'W'.

Extracting Substrings

JavaScript provides the `substring()` method to extract a part of a string. You can specify the starting and ending positions for extracting the substring. Here's an example:

  1. let message = "Hello, World!";
  2. console.log(message.substring(0, 5)); // Output: Hello

In the above example, `message.substring(0, 5)` returns the substring from index 0 to index 4 (exclusive), which is "Hello".

Changing Case

JavaScript has two methods to convert the case of a string: `toUpperCase()` and `toLowerCase()`. These methods return a new string with the desired case. Here's an example:

  1. let name = "John Doe";
  2. console.log(name.toUpperCase()); // Output: JOHN DOE
  3. console.log(name.toLowerCase()); // Output: john doe

In the above example, `name.toUpperCase()` returns the string "JOHN DOE" in uppercase, and `name.toLowerCase()` returns the string "john doe" in lowercase.

Checking if a String Contains a Substring

To check if a string contains a specific substring, you can use the `includes()` method. This method returns a boolean value indicating whether the substring is found within the string. Here's an example:

  1. let message = "Hello, World!";
  2. console.log(message.includes("Hello")); // Output: true
  3. console.log(message.includes("JavaScript")); // Output: false

In the above example, `message.includes("Hello")` returns `true` because the string "Hello" is present in the `message` string. `message.includes("JavaScript")` returns `false` because the string "JavaScript" is not present.

Key Takeaways

  • A string is a sequence of characters enclosed in single or double quotes.

  • JavaScript provides various methods for string manipulation, including concatenation, extracting substrings, converting case, and checking for substrings.

  • String concatenation can be done using the `+` operator or the `concat()` method.

  • The `length` property returns the number of characters in a string.

  • Individual characters within a string can be accessed using square brackets and the index of the character.

  • The `substring()` method allows you to extract a part of a string.

  • The `toUpperCase()` and `toLowerCase()` methods convert the case of a string.

  • The `includes()` method checks if a string contains a specific substring and returns a boolean value.

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