Javascript
In JavaScript, a string is a sequence of characters enclosed in either single (' ') or double (" "`) quotes. Strings are used to represent text and are a fundamental data type in the language. Here’s a simple example:
let greeting = 'Hello, World!';
You can create a string in JavaScript using a string literal, encapsulating the text within single (' ') or double (" ") quotes.
let exampleString = 'Hello, World!';
Alternatively, strings can be created using the String object and the new keyword.
let anotherString = new String('JavaScript Tutorial');
In this example, new is a keyword that is used to create an instance of string.
Here is a list of common string methods in JavaScript!
| Method | Description |
|---|---|
| charAt(index) | Returns the character at the specified index. |
| charCodeAt(index) | Returns the Unicode value of the character at the specified index. |
| concat(…strings) | Combines two or more strings and returns a new string. |
| endsWith(search) | Checks if a string ends with the specified substring and returns a boolean. |
| includes(search) | Checks if a string contains the specified substring and returns a boolean. |
| indexOf(search) | Returns the index of the first occurrence of the specified substring. Returns -1 if the substring is not found. |
| lastIndexOf(search) | Returns the index of the last occurrence of the specified substring. Returns -1 if the substring is not found. |
| length | Returns the length of the string. |
| match(regex) | Searches a string for a specified pattern (regular expression) and returns an array of matches. |
| replace(old, new) | Replaces a specified substring or pattern with another string. |
| search(regex) | Searches a string for a specified pattern and returns the index of the first match. Returns -1 if not found. |
| slice(start, end) | Extracts a portion of a string based on the specified start and end indices. |
| split(separator) | Splits a string into an array of substrings based on a specified separator. |
| startsWith(search) | Checks if a string starts with the specified substring and returns a boolean. |
| substr(start, length) | Extracts a specified number of characters from a string, starting at a specified position. |
| substring(start, end) | Extracts characters between two indices in a string. |
| toLocaleLowerCase() | Converts a string to lowercase based on the host’s current locale. |
| toLocaleUpperCase() | Converts a string to uppercase based on the host’s current locale. |
| toLowerCase() | Converts a string to lowercase. |
| toUpperCase() | Converts a string to uppercase. |
| trim() | Removes whitespace from both ends of a string. |
| valueOf() | Returns the primitive value of a string object. |
The length property in JavaScript is used to get the length (number of characters) of a string. Here’s an example:
let str = 'Hello, World!';
let strLength = str.length;
console.log(strLength); // Outputs: 13
This method returns the character at the specified index in the string.
let str = 'Hello, World!';
let charAtIndex = str.charAt(7);
console.log(charAtIndex); // Outputs: W
The concat method combines two or more strings and returns a new string.
let str1 = 'Hello';
let str2 = 'World';
let combinedString = str1.concat(', ', str2, '!');
console.log(combinedString); // Outputs: Hello, World!
The indexOf method returns the index of the first occurrence of the specified substring.
let str = 'JavaScript is awesome!';
let indexOfIs = str.indexOf('is');
console.log(indexOfIs); // Outputs: 11
The substring method extracts characters between two indices in a string.
let str = 'JavaScript';
let subString = str.substring(4, 6);
console.log(subString); // Outputs: Sc
The replace method replaces a specified substring or pattern with another string.
let str = 'Hello, World!';
let newStr = str.replace('World', 'Universe');
console.log(newStr); // Outputs: Hello, Universe!
The toUpperCase method converts a string to uppercase.
let str = 'hello';
let upperCaseStr = str.toUpperCase();
console.log(upperCaseStr); // Outputs: HELLO
The split method splits a string into an array of substrings based on a specified separator.
let str = 'apple,orange,banana';
let fruitsArray = str.split(',');
console.log(fruitsArray); // Outputs: ['apple', 'orange', 'banana']
You can access individual characters within a string by using square brackets and the character’s index (zero-based):
let word = 'JavaScript';
let firstLetter = word[0]; // J
let thirdLetter = word[2]; // v
These characters are used to include special characters within strings. For example:
let specialString = 'This is a line\nbreak.';
console.log(specialString);
// Outputs:
// This is a line
// break.
Template strings, enclosed in backticks (`), allow for more dynamic and readable string construction, especially when including variables or expressions:
let name = 'Alice';
let greetingMessage = `Hello, ${name}!`;
console.log(greetingMessage); // Outputs: Hello, Alice!