JavaScript is a vital part of web development, and one of its essential data types is the String object. A string represents a sequence of characters used for storing and manipulating text data. Understanding the built-in methods that can be utilized on strings is crucial for any developer. This article will guide you through various String prototype methods in JavaScript, detailing their syntax and providing examples to enhance your learning experience.
I. Introduction
| Concept | Description |
|---|---|
| String Object | A built-in JavaScript object for working with text. |
| Prototype Methods | Inherited methods from the String object that can manipulate string data. |
II. String.prototype.bold()
A. Description
This method returns a new string with the characters wrapped in bold HTML tags.
B. Syntax
string.bold();
C. Example usage
let str = "Hello World!";
let boldStr = str.bold();
console.log(boldStr); // "Hello World!"
III. String.prototype.charAt()
A. Description
This method returns the character at a specified index (position) in a string.
B. Syntax
string.charAt(index);
C. Example usage
let str = "Hello";
console.log(str.charAt(1)); // "e"
IV. String.prototype.charCodeAt()
A. Description
This method returns the Unicode character code of a specified index in a string.
B. Syntax
string.charCodeAt(index);
C. Example usage
let str = "Hello";
console.log(str.charCodeAt(0)); // 72
V. String.prototype.concat()
A. Description
This method joins two or more strings and returns a new string.
B. Syntax
string1.concat(string2, string3, ...);
C. Example usage
let str1 = "Hello";
let str2 = "World!";
let combined = str1.concat(" ", str2);
console.log(combined); // "Hello World!"
VI. String.prototype.indexOf()
A. Description
This method returns the index of the first occurrence of a specified value in a string. Returns -1 if not found.
B. Syntax
string.indexOf(searchValue, startIndex);
C. Example usage
let str = "Hello World!";
let index = str.indexOf("o");
console.log(index); // 4
VII. String.prototype.lastIndexOf()
A. Description
This method returns the index of the last occurrence of a specified value in a string. Returns -1 if not found.
B. Syntax
string.lastIndexOf(searchValue, startIndex);
C. Example usage
let str = "Hello World!";
let lastIndex = str.lastIndexOf("o");
console.log(lastIndex); // 7
VIII. String.prototype.localeCompare()
A. Description
This method compares two strings in the current locale and returns a number indicating whether the reference string occurs before, after, or is the same as the compared string.
B. Syntax
string.localeCompare(compareString);
C. Example usage
let str1 = "apple";
let str2 = "banana";
console.log(str1.localeCompare(str2)); // -1 (first string comes first)
IX. String.prototype.match()
A. Description
This method retrieves the matches when matching a string against a regular expression.
B. Syntax
string.match(regexp);
C. Example usage
let str = "The rain in Spain stays mainly in the plain";
let matches = str.match(/ain/g);
console.log(matches); // ["ain", "ain", "ain"]
X. String.prototype.replace()
A. Description
This method replaces a specified value with another value in a string and returns a new string.
B. Syntax
string.replace(searchValue, newValue);
C. Example usage
let str = "Hello World!";
let newStr = str.replace("World", "JavaScript");
console.log(newStr); // "Hello JavaScript!"
XI. String.prototype.search()
A. Description
This method searches a string for a specified value and returns the position of the match.
B. Syntax
string.search(regexp);
C. Example usage
let str = "The quick brown fox jumps over the lazy dog.";
let position = str.search(/fox/);
console.log(position); // 16
XII. String.prototype.slice()
A. Description
This method extracts a section of a string and returns it as a new string.
B. Syntax
string.slice(startIndex, endIndex);
C. Example usage
let str = "Hello World!";
let sliced = str.slice(0, 5);
console.log(sliced); // "Hello"
XIII. String.prototype.split()
A. Description
This method splits a string into an array of substrings based on a specified delimiter.
B. Syntax
string.split(separator, limit);
C. Example usage
let str = "apple,banana,cherry";
let fruits = str.split(",");
console.log(fruits); // ["apple", "banana", "cherry"]
XIV. String.prototype.substring()
A. Description
This method returns a portion of a string, between two specified indices.
B. Syntax
string.substring(startIndex, endIndex);
C. Example usage
let str = "Hello World!";
let subStr = str.substring(0, 5);
console.log(subStr); // "Hello"
XV. String.prototype.toLowerCase()
A. Description
This method returns the calling string value converted to lowercase.
B. Syntax
string.toLowerCase();
C. Example usage
let str = "HELLO WORLD!";
let lowerStr = str.toLowerCase();
console.log(lowerStr); // "hello world!"
XVI. String.prototype.toUpperCase()
A. Description
This method returns the calling string value converted to uppercase.
B. Syntax
string.toUpperCase();
C. Example usage
let str = "hello world!";
let upperStr = str.toUpperCase();
console.log(upperStr); // "HELLO WORLD!"
XVII. String.prototype.trim()
A. Description
This method removes whitespace from both ends of a string.
B. Syntax
string.trim();
C. Example usage
let str = " Hello World! ";
let trimmedStr = str.trim();
console.log(trimmedStr); // "Hello World!"
XVIII. Frequently Asked Questions (FAQ)
1. What are prototype methods in JavaScript?
Prototype methods are functions that are attached to JavaScript objects. For strings, these methods enable various string manipulations.
2. How do I determine the length of a string?
You can use the length property: string.length.
3. Are string methods case-sensitive?
Yes, string methods like indexOf are case-sensitive. “Hello” and “hello” would return different results.
4. Can I modify a string in JavaScript?
No, strings are immutable in JavaScript. However, you can create a new string based on modifications of the original string.
5. How do I convert a number to a string?
You can use the toString() method: let numStr = number.toString();
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