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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Numbers are used to represent both integer and floating-point values.

Numbers are most commonly expressed in literal forms like 255 or 3.14159 ↴

let num1 = 5; → number

let num2 = 2.5; → number

let num3 = num1 + num2;

console.log(num3); returns ↴

7.5 → number

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Alternate case of each character in string using ↴

for loop → executes a block of code a number of times.

toLowerCase() method → returns the value of the string converted to lower case.

toUpperCase() method → returns the value of the string converted to upper case.

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for loop repeatedly executes a block of code until a specified condition evaluates to false.

The loop runs a block of code a set number of times, defined by an initialization, a condition, and an increment.

for (let x = 0; x < 4; x++) {

console.log(x);

}

Loop variable x is initialized to 0

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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toLowerCase() method converts all letters to lower case. The original string is unchanged.

const str3 = "hELlo wORLd";

str3.toLowerCase(); returns ↴

"hello world" → lower case

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toUpperCase() method converts all letters to upper case. The original string is unchanged.

const str4 = "hELlo wORLd";

str4.toUpperCase(); returns ↴

"HELLO WORLD" → upper case

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Initialize a variable to hold the string to alternate case.

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Define a function inverseCase to inverse the case of each character in a string.

function inverseCase(str) {}

The function takes a string as input str and returns a new string with the case of all characters inverted. The original string remains unchanged.

Initialize an empty string to hold the new characters.

let newStr = "" newStr

Loop through each character str[x] in the input string.

for (let x = 0; x < str.length; x++) {}

Check if the current character str[x] is upper case.

if (str[x] === str[x].toUpperCase()) {}

If it is upper case, convert it to lower case and add to newStr

newStr += str[x].toLowerCase()

else, If it is lower case, convert it to upper case and add to newStr

newStr += str[x].toUpperCase()

Return the newly constructed string with inverted cases.

return newStr

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Call the function with ↴

inverseCase(string1);

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Inverse case of each character in a string.