Modern JavaScript (ES2021)

Numeric Separators

Make numbers readable - use underscores like commas!

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What are Numeric Separators?

Numeric separators let you use _ (underscore) in numbers to improve readability! Just like using commas in written numbers (1,000,000), you can write1_000_000 in code. The underscores are ignored at runtime - purely visual!

Readability Matters!

Which is easier to read: 1000000 or1_000_000? Separators make large numbers instantly clear!

Example 1: Making Numbers Readable

Use underscores anywhere in numbers for clarity

javascript

code

DarkEditable

// Large numbers - much clearer!
const million = 1_000_000;
const billion = 1_000_000_000;
const trillion = 1_000_000_000_000;

console.log(million);   // 1000000
console.log(billion);   // 1000000000
console.log(trillion);  // 1000000000000

// Financial amounts
const salary = 75_000;
const price = 1_299_99;  // $1,299.99
const budget = 50_000_000;

console.log(`Salary: $${salary}`);  // Salary: $75000

// Binary numbers (group by 4 or 8)
const permissions = 0b1111_1010_0011_1100;
const flags = 0b1010_1010;

console.log(permissions);  // 64060
console.log(flags);        // 170

// Hexadecimal colors (group by color channel)
const color = 0xFF_00_FF;  // Magenta (R_G_B)
const white = 0xFF_FF_FF;

console.log(color.toString(16));  // "ff00ff"

// Scientific notation
const planckConstant = 6.626_070_15e-34;
const speedOfLight = 299_792_458;  // m/s

console.log(planckConstant);  // 6.62607015e-34

// Decimals
const pi = 3.14_15_92_65;
const price2 = 19.99;  // Can use, but less common

console.log(pi);  // 3.14159265

Console Output

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

Example 2: Real-World Use Cases

Practical scenarios for numeric separators

javascript

code

DarkEditable

// 1. Configuration values
const config = {
  maxFileSize: 10_000_000,      // 10 MB
  timeout: 30_000,               // 30 seconds
  retryLimit: 5_000,             // 5k attempts
  cacheSize: 100_000_000         // 100 million entries
};

// 2. Database IDs and timestamps
const userId = 123_456_789;
const timestamp = 1_702_589_123_456;  // Milliseconds since epoch

// 3. Financial calculations
function calculateLoan(principal, rate, years) {
  const monthlyRate = rate / 12 / 100;
  const payments = years * 12;
  
  return principal * monthlyRate / 
    (1 - Math.pow(1 + monthlyRate, -payments));
}

const loanAmount = 250_000;  // $250,000
const monthlyPayment = calculateLoan(loanAmount, 3.5, 30);
console.log(`Monthly: $${monthlyPayment.toFixed(2)}`);

// 4. Bit manipulation
const READ    = 0b0000_0100;  // 4
const WRITE   = 0b0000_0010;  // 2
const EXECUTE = 0b0000_0001;  // 1

const permissions = READ | WRITE;  // 6
console.log(`Permissions: ${permissions.toString(2)}`);

// 5. Large array sizes
const BUFFER_SIZE = 1_048_576;  // 1 MB
const buffer = new ArrayBuffer(BUFFER_SIZE);

console.log(`Buffer size: ${BUFFER_SIZE.toLocaleString()} bytes`);

// 6. Credit card numbers (just for display, not storage!)
// Note: Don't store card numbers like this in real code!
const displayNumber = '4532_1234_5678_9010';
console.log(displayNumber);

Console Output

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

⚠️Rules & Restrictions

✅ Allowed

• 1_000_000 - Between digits

• 0xFF_00_FF - In hex

• 0b1111_0000 - In binary

• 3.14_15 - In decimals

❌ Not Allowed

• _1000 - At start

• 1000_ - At end

• 1__000 - Multiple consecutive

• 3._14 - After decimal point

• 1e_5 - Before/after 'e'

Key Takeaways

Underscore

Use _ anywhere between digits for readability

👁️

Visual Only

Ignored at runtime - doesn't change value

🔢

All Formats

Works with decimal, hex, binary, octal, BigInt

💡

ES2021

Modern readability feature

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&&=, ||=, ??= operators for conditional assignment (ES2021).

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Returns first fulfilled promise, ignoring rejections (ES2021).

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Output

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Modern JavaScript (ES2021)

Numeric Separators

Make numbers readable - use underscores like commas!

Find videos you like?

Save to resource drawer for future reference!

What are Numeric Separators?

Readability Matters!

Which is easier to read: 1000000 or1_000_000? Separators make large numbers instantly clear!

Example 1: Making Numbers Readable

Use underscores anywhere in numbers for clarity

javascript

code

DarkEditable

// Large numbers - much clearer!
const million = 1_000_000;
const billion = 1_000_000_000;
const trillion = 1_000_000_000_000;

console.log(million);   // 1000000
console.log(billion);   // 1000000000
console.log(trillion);  // 1000000000000

// Financial amounts
const salary = 75_000;
const price = 1_299_99;  // $1,299.99
const budget = 50_000_000;

console.log(`Salary: $${salary}`);  // Salary: $75000

// Binary numbers (group by 4 or 8)
const permissions = 0b1111_1010_0011_1100;
const flags = 0b1010_1010;

console.log(permissions);  // 64060
console.log(flags);        // 170

// Hexadecimal colors (group by color channel)
const color = 0xFF_00_FF;  // Magenta (R_G_B)
const white = 0xFF_FF_FF;

console.log(color.toString(16));  // "ff00ff"

// Scientific notation
const planckConstant = 6.626_070_15e-34;
const speedOfLight = 299_792_458;  // m/s

console.log(planckConstant);  // 6.62607015e-34

// Decimals
const pi = 3.14_15_92_65;
const price2 = 19.99;  // Can use, but less common

console.log(pi);  // 3.14159265

Console Output

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

Example 2: Real-World Use Cases

Practical scenarios for numeric separators

javascript

code

DarkEditable

// 2. Database IDs and timestamps
const userId = 123_456_789;
const timestamp = 1_702_589_123_456;  // Milliseconds since epoch

const loanAmount = 250_000;  // $250,000
const monthlyPayment = calculateLoan(loanAmount, 3.5, 30);
console.log(`Monthly: $${monthlyPayment.toFixed(2)}`);

// 4. Bit manipulation
const READ    = 0b0000_0100;  // 4
const WRITE   = 0b0000_0010;  // 2
const EXECUTE = 0b0000_0001;  // 1

const permissions = READ | WRITE;  // 6
console.log(`Permissions: ${permissions.toString(2)}`);

// 5. Large array sizes
const BUFFER_SIZE = 1_048_576;  // 1 MB
const buffer = new ArrayBuffer(BUFFER_SIZE);

console.log(`Buffer size: ${BUFFER_SIZE.toLocaleString()} bytes`);

// 6. Credit card numbers (just for display, not storage!)
// Note: Don't store card numbers like this in real code!
const displayNumber = '4532_1234_5678_9010';
console.log(displayNumber);

Console Output

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

⚠️Rules & Restrictions

✅ Allowed

• 1_000_000 - Between digits

• 0xFF_00_FF - In hex

• 0b1111_0000 - In binary

• 3.14_15 - In decimals

❌ Not Allowed

• _1000 - At start

• 1000_ - At end

• 1__000 - Multiple consecutive

• 3._14 - After decimal point

• 1e_5 - Before/after 'e'

Key Takeaways

Underscore

Use _ anywhere between digits for readability

👁️

Visual Only

Ignored at runtime - doesn't change value

🔢

All Formats

Works with decimal, hex, binary, octal, BigInt

💡

ES2021

Modern readability feature

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Logical Assignment

Promise.any

JavaScript Code Editor

Building Your Learning Module...

Numeric Separators

What are Numeric Separators?

Readability Matters!

Example 1: Making Numbers Readable

Example 2: Real-World Use Cases

✅ Allowed

❌ Not Allowed

Key Takeaways

Underscore

Visual Only

All Formats

ES2021

Logical Assignment

Promise.any

JavaScript Code Editor

Numeric Separators

What are Numeric Separators?

Readability Matters!

Example 1: Making Numbers Readable

Example 2: Real-World Use Cases

✅ Allowed

❌ Not Allowed

Key Takeaways

Underscore

Visual Only

All Formats

ES2021