Core JavaScript (Basics)

20 Exercises Available

Variables, operators, type conversion, template strings — build a strong foundation.

Safe Number Input (string → number) + Sum

Create a function `sum(a, b)` that accepts inputs as string or number. The function should strictly convert to number and return the sum. Return `null` for invalid input. Example: - sum("10", "5") → 15 - sum("10a", 5) → null

Sample Output:

sum("10","5") => 15
sum("10a",5) => null

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2.Easy

Price After Discount (round to 2 decimals)

Create a function `finalPrice(price, discountPercent)`. Apply discount and return the final price. Output should be rounded to 2 decimals. Example: - finalPrice(999, 12.5) → 874.13

Sample Output:

finalPrice(999, 12.5) => 874.13
finalPrice(1000, 20) => 800

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3.Easy

Template String: User Greeting

Create a function `greet(name, city)` that returns a sentence with trimmed name/city: `Hi <name>! Welcome to <city>.` Note: Use `Guest` if name/city is blank.

Sample Output:

greet("  Alice  ", "Mumbai") => "Hi Alice! Welcome to Mumbai."
greet(null, "") => "Hi Guest! Welcome to Guest."

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4.Easy

Clamp Number in Range (min/max)

Create a function `clamp(n, min, max)` that fixes a number within a range. Example: - clamp(120, 0, 100) → 100 - clamp(-5, 0, 100) → 0

Sample Output:

clamp(120, 0, 100) => 100
clamp(-5, 0, 100) => 0
clamp(50, 0, 100) => 50

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5.Medium

Truthy/Falsy: Is Field Filled?

Function `isFilled(value)` banao jo true tab return kare jab value meaningful ho: - string: trimmed length > 0 - number: finite - boolean: true - others: false

Sample Output:

isFilled("hello") => true
isFilled("  ") => false
isFilled(5) => true
isFilled(NaN) => false

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6.Medium

Parse Integer Safely (with radix)

Create a function `parseIntSafe(str, radix=10)` that converts a string to integer. Return null for invalid input. Support radix parameter. Example: - parseIntSafe("123") → 123 - parseIntSafe("0xFF", 16) → 255 - parseIntSafe("abc") → null

Sample Output:

parseIntSafe("123") => 123
parseIntSafe("0xFF", 16) => 255
parseIntSafe("1010", 2) => 10
parseIntSafe("abc") => null

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7.Medium

Format Currency (Indian Format)

Create a function `formatCurrency(amount)` that converts a number to Indian currency format. Example: 1234567 → "12,34,567" Note: Indian numbering system uses lakhs/crores.

Sample Output:

formatCurrency(1234567) => "12,34,567"
formatCurrency(10000000) => "1,00,00,000"
formatCurrency(-5000) => "5,000"

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8.Easy

Generate Random String (alphanumeric)

Create a function `randomString(length=8)` that generates a random alphanumeric string. Example: randomString(6) → "a3B9x2"

Sample Output:

randomString(6) => "a3B9x2" (random)
randomString(10) => "Xy7mN2pQ9k" (random)
randomString(4) => "K9mP" (random)

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9.Medium

Check if Number is Prime

Create a function `isPrime(n)` that checks if a number is prime. Example: - isPrime(7) → true - isPrime(10) → false

Sample Output:

isPrime(7) => true
isPrime(10) => false
isPrime(2) => true
isPrime(1) => false

View Solution

10.Medium

Calculate Age from Date of Birth

Create a function `calculateAge(dob)` that calculates age from date of birth. Example: calculateAge("1990-05-15") → 34 (assuming current year is 2024)

Sample Output:

calculateAge("1990-05-15") => 34 (if current date is 2024-06-01)
calculateAge("2000-12-25") => 23 (if current date is 2024-01-01)

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11.Hard

Deep Clone Object (without JSON)

Create a function `deepClone(obj)` that deeply clones an object. Do not use JSON methods. Example: deepClone({a: 1, b: {c: 2}}) → {a: 1, b: {c: 2}} (new object)

Sample Output:

deepClone({a: 1, b: {c: 2}}) => {a: 1, b: {c: 2}} (new object)
const obj = {x: 1}; const cloned = deepClone(obj); obj.x = 2; cloned.x => 1

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12.Hard

Throttle Function (rate limiting)

Create a function `throttle(fn, delay)` that throttles a function. If multiple calls occur within delay, only the first call executes. Example: Throttled function with 500ms delay, 3 rapid calls → only 1st call executes

Sample Output:

const throttled = throttle(() => console.log("called"), 500);
throttled(); throttled(); throttled();
// Only first call executes, others ignored within 500ms

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13.Hard

Check if Two Objects are Equal (deep)

Create a function `deepEqual(a, b)` that deeply compares if two objects are equal. Example: deepEqual({a: 1, b: {c: 2}}, {a: 1, b: {c: 2}}) → true

Sample Output:

deepEqual({a: 1, b: {c: 2}}, {a: 1, b: {c: 2}}) => true
deepEqual({a: 1}, {a: 2}) => false
deepEqual({x: 1, y: 2}, {x: 1}) => false

View Solution

14.Easy

Format Phone Number (Indian Format)

Create a function `formatPhone(phone)` that converts a 10-digit number to Indian format. Example: formatPhone("9876543210") → "+91 98765 43210"

Sample Output:

formatPhone("9876543210") => "+91 98765 43210"
formatPhone("+91-98765-43210") => "+91 98765 43210"

View Solution

15.Easy

Calculate Percentage

Create a function `percentage(value, total)` that calculates percentage. Round the result to 2 decimals. Example: percentage(25, 200) → 12.5

Sample Output:

percentage(25, 200) => 12.5
percentage(75, 300) => 25
percentage(1, 3) => 33.33

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16.Medium

Generate UUID v4 (simple)

Create a function `generateUUID()` that generates a UUID v4 format string. Example: generateUUID() → "550e8400-e29b-41d4-a716-446655440000" (format)

Sample Output:

generateUUID() => "550e8400-e29b-41d4-a716-446655440000" (format, random)
generateUUID() => "a1b2c3d4-e5f6-4789-a012-b3c4d5e6f789" (format, random)

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17.Medium

Check if String is Valid Email

Create a function `isValidEmail(email)` that validates email using regex. Example: - isValidEmail("test@example.com") → true - isValidEmail("invalid") → false

Sample Output:

isValidEmail("test@example.com") => true
isValidEmail("invalid") => false
isValidEmail("user@domain.co.in") => true

View Solution

18.Medium

Convert Seconds to Human Readable Time

Create a function `formatDuration(seconds)` that converts seconds to "Xh Ym Zs" format. Example: formatDuration(3665) → "1h 1m 5s"

Sample Output:

formatDuration(3665) => "1h 1m 5s"
formatDuration(125) => "2m 5s"
formatDuration(45) => "45s"

View Solution

19.Easy

Find Maximum Number in Array

Create a function `findMax(arr)` that finds the maximum number in an array. Return null for empty array. Example: findMax([3, 7, 2, 9, 1]) → 9

Sample Output:

findMax([3, 7, 2, 9, 1]) => 9
findMax([-5, -2, -10]) => -2
findMax([]) => null

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20.Easy

Check if Number is Even or Odd

Create functions `isEven(n)` and `isOdd(n)` that check if a number is even or odd. Example: - isEven(4) → true - isOdd(5) → true

Sample Output:

isEven(4) => true
isOdd(5) => true
isEven(3) => false
isOdd(2) => false

View Solution

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