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Strings in JavaScript are sequences of characters used to represent text. They are primitive data types but have object-like behavior due to JavaScript's automatic boxing (temporary conversion to a String object when methods are called). Strings are immutable, meaning once created, their values cannot be changed.

Key Characteristics:

• Strings can be created using single quotes ('), double quotes ("), or backticks (`).
• Backticks enable template literals, which support multi-line strings and string interpolation.
• Strings are zero-indexed, meaning the first character is at index 0.
• Strings have a length property that returns the number of characters in the string.

Common String Methods (with TypeScript Signatures):

1. charAt(): Returns the character at the specified index.
   • Signature: charAt(index: number): string;
2. charCodeAt(): Returns the Unicode value of the character at the specified index.
   • Signature: charCodeAt(index: number): number;
3. concat(): Combines two or more strings and returns a new string.
   • Signature: concat(...strings: string[]): string;
4. includes(): Checks if a string contains a specified substring.
   • Signature: includes(searchString: string, position?: number): boolean;
5. indexOf(): Returns the index of the first occurrence of a specified substring, or -1 if not found.
   • Signature: indexOf(searchString: string, position?: number): number;
6. lastIndexOf(): Returns the index of the last occurrence of a specified substring, or -1 if not found.
   • Signature: lastIndexOf(searchString: string, position?: number): number;
7. slice(): Extracts a section of a string and returns it as a new string.
   • Signature: slice(start?: number, end?: number): string;
8. substring(): Similar to slice(), but does not support negative indices.
   • Signature: substring(start: number, end?: number): string;
9. substr(): Extracts a specified number of characters starting from a specified index.
   • Signature: substr(start: number, length?: number): string;
10. toLowerCase(): Converts the string to lowercase.
    • Signature: toLowerCase(): string;
11. toUpperCase(): Converts the string to uppercase.
    • Signature: toUpperCase(): string;
12. trim(): Removes whitespace from both ends of a string.
    • Signature: trim(): string;
13. replace(): Replaces a specified substring or pattern with another substring.
    • Signature: replace(searchValue: string | RegExp, replaceValue: string): string;
14. split(): Splits a string into an array of substrings based on a specified separator.
    • Signature: split(separator: string | RegExp, limit?: number): string[];
15. startsWith(): Checks if a string starts with a specified substring.
    • Signature: startsWith(searchString: string, position?: number): boolean;
16. endsWith(): Checks if a string ends with a specified substring.
    • Signature: endsWith(searchString: string, position?: number): boolean;
17. match(): Searches a string for a match against a regular expression and returns the matches.
    • Signature: match(regexp: string | RegExp): RegExpMatchArray | null;
18. repeat(): Returns a new string with the original string repeated a specified number of times.
    • Signature: repeat(count: number): string;

Template Literals:

• Template literals (using backticks) allow embedded expressions and multi-line strings.
• Example:

  const name = "Alice";
  const greeting = `Hello, ${name}!
  Welcome to JavaScript.`;
  console.log(greeting);
  

Linked Cards:

• Data Types in JavaScript: Strings are a primitive data type in JavaScript.
• Functions in JavaScript: String methods are functions that operate on strings.
• Arrays in JavaScript: Strings can be converted to arrays using split().
• Regular Expressions in JavaScript: Used with methods like match() and replace().
• Prototypes in JavaScript: Strings inherit methods from String.prototype.
• Syntactic Sugar: Template literals provide syntactic sugar for string manipulation.

Tags: #JavaScript #Strings #Methods #TemplateLiterals #TypeScript #DataTypes

Connections:

Sources:

• From: Una breve guía a la programación y JavaScript