Introduction to Strings
In JavaScript, a string is a sequence of characters used to represent text.
Strings are enclosed in either single quotes ' ', double quotes " ", or backticks ` `.
Importantly, strings are immutable – once created, their characters cannot be changed.
String Methods
Below is a table of many commonly used string methods along with short descriptions and example usage notes.
| Method | Description & Example |
|---|---|
| length | Returns string length. E.g., "hello".length // 5 |
| slice(start, end) | Extracts substring. E.g., "hello".slice(1, 4) // "ell" |
| substring(start, end) | Similar to slice but doesn't allow negative indexes. E.g., "hello".substring(1, 4) // "ell" |
| substr(start, length) | Extracts part of string with specified length. E.g., "hello".substr(1, 3) // "ell" |
| toUpperCase() | Converts to uppercase. E.g., "hello".toUpperCase() // "HELLO" |
| toLowerCase() | Converts to lowercase. E.g., "HELLO".toLowerCase() // "hello" |
| concat() | Concatenates strings. E.g., "Hello".concat(" ", "World") // "Hello World" |
| trim() | Removes spaces from both ends. E.g., " hello ".trim() // "hello" |
| indexOf(substring) | Returns first index of substring. E.g., "hello".indexOf("l") // 2 |
| lastIndexOf(substring) | Returns last index of substring. E.g., "hello".lastIndexOf("l") // 3 |
| includes(substring) | Checks if substring exists. E.g., "hello".includes("ll") // true |
| startsWith(substring) | Checks if string starts with substring. E.g., "hello".startsWith("he") // true |
| endsWith(substring) | Checks if string ends with substring. E.g., "hello".endsWith("lo") // true |
| replace(old, new) | Replaces first occurrence of a substring. E.g., "hello".replace("l", "p") // "heplo" |
| replaceAll(old, new) | Replaces all occurrences. E.g., "hello".replaceAll("l", "p") // "heppo" |
| split(separator) | Splits string into an array. E.g., "a,b,c".split(",") // ["a","b","c"] |
| charAt(index) | Returns character at index. E.g., "hello".charAt(1) // "e" |
| charCodeAt(index) | Returns Unicode value at index. E.g., "A".charCodeAt(0) // 65 |
Q35. Print Each Character on a New Line
// Q35: Print each character on a new line
let prompt = require("prompt-sync")();
let str = prompt("Enter a string: ");
for (let i = 0; i < str.length; i++) {
console.log(str[i]);
}
Note: In a browser, use prompt() and console.log() for demonstration.
Q36. Reverse the String
// Q36: Reverse a string
let prompt = require("prompt-sync")();
let str = prompt("Enter a string: ");
let reversed = "";
for (let i = str.length - 1; i >= 0; i--) {
reversed += str[i];
}
console.log("Reversed string:", reversed);
In the browser, you can output the reversed string using alert() or DOM manipulation.
Interactive Demo: Try Out String Methods
Enter a string and choose a method to see its effect. Additional parameter inputs will appear as needed.