Strings are a sequence of zero or more characters written inside quotes used to represent text.

Strings may consist of letters, numbers, symbols, words, or sentences.

Strings are immutable, they cannot be changed.

Each character in a string has an index.

The first character will be index 0 the second character will be index 1 and so on.

There are two ways to access an individual character in a string.

charAt() method

const str1 = "abc"; string

str1.charAt(0); character at index 0 → "a"

str1.charAt(1); character at index 1 → "b"

str1.charAt(2); character at index 2 → "c"

str1.charAt(3); character at index 3 → "" index not found

Alternatively use at() or slice() methods

bracket notation []

const str2 = "abc"; string

str2[0]; character at index 0 → "a"

str2[1]; character at index 1 → "b"

str2[2]; character at index 2 → "c"

str2[3]; character at index 3 → undefined index not found

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Reverse a string using a while loop

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while loop repeatedly executes a block of code as long as a specified condition evaluates to true.

while (condition) {

// execute code as long as condition is true

}

let x = 0; → counter

while (x < 4) {

console.log(x);

x++;

}

Initialize a counter variable x outside of the loop.

Condition x < 4 is checked before each iteration.

The loop will continue to run as long as x is less than 4

The loop repeatedly executes a block of code 4 times, from 0 to 3

For each iteration of the loop, the current value of x is printed to the console.

After each iteration, x is incremented by 1 x++

When x reaches 4 the condition evaluates to false, terminating the loop.

0

1

2

3 → printed to console

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length property returns the number of characters in a string.

const str3 = "Hello World";

str3.length; returns ↴

11 → there are 11 characters in the string

Strings are zero indexed, the first character will be index 0

The last character will be at index length -1

To find the last index in a string.

const str4 = "Hello World";

str4.length - 1; returns ↴

10 → end index of string

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Initialize a variable to hold the string to be reversed.

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Define a function reverseString to reverse a string.

function reverseString(str) {}

The function takes a string as input str and returns a new string with the characters reversed.

Variable to hold the reversed string.

let reversed = "" reversed

Start from the last character of the string.

let index = str.length - 1 index

Loop while index is non-negative.

while (index >= 0) {}

Append the current character str[index] to reversed

reversed += str[index]

Move to the previous character

index-- Decrement by 1

Loop terminates when index is negative.

Return the reversed string.

return reversed

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Call the function with ↴

reverseString(string1);

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Reverse a string.

str = "Hello"

Iteration starts from the last character of the string.

let index = str.length - 1

while (index >= 0)

reversed = "" empty string to hold the reversed string.

During each iteration, the current character str[index] will be appended to reversed at the end of the string ↴

Loop exits when condition is false.

The reversed string "olleH" is returned.

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Reverse a string.

const string1 = "Hello World";

function reverseString(str) {

let reversed = "";

let index = str.length - 1;

while (index >= 0) {

reversed += str[index];

index--;

}

return reversed;

}

call function

reverseString(string1); returns ↴

"dlroW olleH"