JavaScript Math & Numbers

Number Methods

Convert, format, and validate numbers

Find videos you like?

Save to resource drawer for future reference!

Working with Numbers

JavaScript provides methods to convert, format, and validate numbers. Perfect for parsing user input, formatting display values, and checking number validity.

Number() - Convert to Number

Convert strings and other types to numbers

javascript

code

DarkEditable

Console Output

Click "Run Code" to see output here...

parseInt() & parseFloat()

Parse strings to integers or decimals

javascript

code

DarkEditable

Console Output

Click "Run Code" to see output here...

toFixed() - Format Decimals

Round to specific decimal places (returns string)

javascript

code

DarkEditable

Console Output

Click "Run Code" to see output here...

toPrecision() - Significant Digits

Format to specific number of significant figures

javascript

code

DarkEditable

Console Output

Click "Run Code" to see output here...

toString() - Convert to String

Convert number to string with optional base

javascript

code

DarkEditable

Console Output

Click "Run Code" to see output here...

isNaN() & isFinite()

Check if value is a valid number

javascript

code

DarkEditable

// isNaN - checks if value is NaN
console.log(isNaN(123));           // false (valid number)
console.log(isNaN("hello"));       // true (not a number)
console.log(isNaN(NaN));           // true
console.log(isNaN(undefined));     // true

// Number.isNaN (more strict - doesn't convert)
console.log(Number.isNaN(NaN));    // true
console.log(Number.isNaN("hello"));// false (no conversion)
console.log(Number.isNaN(123));    // false

// isFinite - checks if number is finite
console.log(isFinite(123));        // true
console.log(isFinite(Infinity));   // false
console.log(isFinite(-Infinity));  // false
console.log(isFinite(NaN));        // false
console.log(isFinite("123"));      // true (converts)

// Number.isFinite (more strict)
console.log(Number.isFinite(123)); // true
console.log(Number.isFinite("123")); // false (no conversion)

// Validate user input
function isValidNumber(value) {
  return !isNaN(value) && isFinite(value);
}

console.log(isValidNumber(42));    // true
console.log(isValidNumber("abc")); // false
console.log(isValidNumber(Infinity)); // false

Console Output

Click "Run Code" to see output here...

Number.isInteger()

Check if number is an integer

javascript

code

DarkEditable

Console Output

Click "Run Code" to see output here...

Number Constants

Useful number limits and special values

javascript

code

DarkEditable

Console Output

Click "Run Code" to see output here...

Quick Reference

Convert

Number() - any to number

parseInt() - to integer

parseFloat() - to decimal

Format

toFixed(n) - n decimals

toPrecision(n) - n digits

toString(base) - to string

Validate

isNaN() - check NaN

isFinite() - check finite

isInteger() - check integer

Key Takeaways

Conversion

Use Number(), parseInt(), or parseFloat()

📝

Formatting

toFixed() returns string, convert back if needed

✅

Validation

Use Number.isNaN() for strict checks

⚠️

Watch Out

parseInt("10px") = 10, not NaN!

Previous Topic

Math Object

Mathematical operations and constants.

Next Topic

Random Numbers

Generating random numbers and ranges.

Ask a Question

Have a question about Number Methods? Ask our AI assistant.

🔐 Login to use AI Assistant

JavaScript Code Editor

Write and experiment with JavaScript code.

Output

Click "Run Code" to see the output.

JavaScript Math & Numbers

Number Methods

Convert, format, and validate numbers

Find videos you like?

Save to resource drawer for future reference!

Working with Numbers

JavaScript provides methods to convert, format, and validate numbers. Perfect for parsing user input, formatting display values, and checking number validity.

Number() - Convert to Number

Convert strings and other types to numbers

javascript

code

DarkEditable

Console Output

Click "Run Code" to see output here...

parseInt() & parseFloat()

Parse strings to integers or decimals

javascript

code

DarkEditable

Console Output

Click "Run Code" to see output here...

toFixed() - Format Decimals

Round to specific decimal places (returns string)

javascript

code

DarkEditable

Console Output

Click "Run Code" to see output here...

toPrecision() - Significant Digits

Format to specific number of significant figures

javascript

code

DarkEditable

Console Output

Click "Run Code" to see output here...

toString() - Convert to String

Convert number to string with optional base

javascript

code

DarkEditable

Console Output

Click "Run Code" to see output here...

isNaN() & isFinite()

Check if value is a valid number

javascript

code

DarkEditable

// Number.isNaN (more strict - doesn't convert)
console.log(Number.isNaN(NaN));    // true
console.log(Number.isNaN("hello"));// false (no conversion)
console.log(Number.isNaN(123));    // false

// Number.isFinite (more strict)
console.log(Number.isFinite(123)); // true
console.log(Number.isFinite("123")); // false (no conversion)

// Validate user input
function isValidNumber(value) {
  return !isNaN(value) && isFinite(value);
}

console.log(isValidNumber(42));    // true
console.log(isValidNumber("abc")); // false
console.log(isValidNumber(Infinity)); // false

Console Output

Click "Run Code" to see output here...

Number.isInteger()

Check if number is an integer

javascript

code

DarkEditable

Console Output

Click "Run Code" to see output here...

Number Constants

Useful number limits and special values

javascript

code

DarkEditable

Console Output

Click "Run Code" to see output here...

Quick Reference

Convert

Number() - any to number

parseInt() - to integer

parseFloat() - to decimal

Format

toFixed(n) - n decimals

toPrecision(n) - n digits

toString(base) - to string

Validate

isNaN() - check NaN

isFinite() - check finite

isInteger() - check integer

Key Takeaways

Conversion

Use Number(), parseInt(), or parseFloat()

📝

Formatting

toFixed() returns string, convert back if needed

✅

Validation

Use Number.isNaN() for strict checks

⚠️

Watch Out

parseInt("10px") = 10, not NaN!

Coder Pod - Learn Programming Online | AI Coding Tutor & Interview Practice

Math Object

Random Numbers

JavaScript Code Editor

Building Your Learning Module...

Number Methods

Working with Numbers

Number() - Convert to Number

parseInt() & parseFloat()

toFixed() - Format Decimals

toPrecision() - Significant Digits

toString() - Convert to String

isNaN() & isFinite()

Number.isInteger()

Number Constants

Key Takeaways

Conversion

Formatting

Validation

Watch Out

Math Object

Random Numbers

JavaScript Code Editor

Number Methods

Working with Numbers

Number() - Convert to Number

parseInt() & parseFloat()

toFixed() - Format Decimals

toPrecision() - Significant Digits

toString() - Convert to String

isNaN() & isFinite()

Number.isInteger()

Number Constants

Key Takeaways

Conversion

Formatting

Validation

Watch Out