Global Functions

Number(value: any): number | NumberObject

// Convert to number
const num1 = Number('42');      // 42
const num2 = Number('3.14');    // 3.14
const num3 = Number(true);      // 1
const num4 = Number(false);     // 0
const num5 = Number(null);      // 0
const num6 = Number(undefined); // NaN

// Create Number object
const obj = new Number(42);
console.log(typeof obj);        // 'object'
console.log(obj.valueOf());     // 42

String(value: any): string | StringObject

// Convert to string
const str1 = String(42);        // '42'
const str2 = String(true);      // 'true'
const str3 = String(null);      // 'null'
const str4 = String(undefined); // 'undefined'
const str5 = String([1,2,3]);   // '1,2,3'

// Create String object
const obj = new String('hello');
console.log(typeof obj);        // 'object'
console.log(obj.valueOf());     // 'hello'

Boolean(value: any): boolean | BooleanObject

// Convert to boolean
const bool1 = Boolean(1);        // true
const bool2 = Boolean(0);        // false
const bool3 = Boolean('hello');  // true
const bool4 = Boolean('');       // false
const bool5 = Boolean(null);     // false
const bool6 = Boolean({});       // true

// Create Boolean object
const obj = new Boolean(true);
console.log(typeof obj);         // 'object'
console.log(obj.valueOf());      // true

parseInt(string: string, radix?: number): number

// Decimal
parseInt('42');           // 42
parseInt('42.7');         // 42 (fractional part ignored)
parseInt('  42  ');       // 42 (whitespace trimmed)

// Different bases
parseInt('1010', 2);      // 10 (binary)
parseInt('10', 8);        // 8 (octal)
parseInt('2a', 16);       // 42 (hexadecimal)
parseInt('z', 36);        // 35 (base 36)

// Invalid inputs
parseInt('hello');        // NaN
parseInt('12abc');        // 12 (stops at non-digit)

parseFloat(string: string): number

parseFloat('3.14');       // 3.14
parseFloat('3.14159');    // 3.14159
parseFloat('  2.5  ');    // 2.5
parseFloat('10');         // 10
parseFloat('1e3');        // 1000
parseFloat('1.5e2');      // 150

// Invalid inputs
parseFloat('hello');      // NaN
parseFloat('3.14abc');    // 3.14 (stops at non-numeric)

isNaN(value: any): boolean

isNaN(NaN);           // true
isNaN('hello');       // true (coerces to NaN)
isNaN(undefined);     // true (coerces to NaN)
isNaN({});            // true (coerces to NaN)

isNaN(42);            // false
isNaN('42');          // false (coerces to 42)
isNaN(true);          // false (coerces to 1)

isFinite(value: any): boolean

isFinite(42);         // true
isFinite(0);          // true
isFinite(-42);        // true
isFinite('42');       // true (coerces to 42)

isFinite(Infinity);   // false
isFinite(-Infinity);  // false
isFinite(NaN);        // false
isFinite('hello');    // false (coerces to NaN)

encodeURI(uri: string): string

const uri = 'https://example.com/path?query=hello world';
const encoded = encodeURI(uri);
console.log(encoded);
// 'https://example.com/path?query=hello%20world'

// Characters NOT encoded: A-Z a-z 0-9 - _ . ! ~ * ' ( )
// Also NOT encoded: ; / ? : @ & = + $ , #

decodeURI(encodedURI: string): string

const encoded = 'https://example.com/path?query=hello%20world';
const decoded = decodeURI(encoded);
console.log(decoded);
// 'https://example.com/path?query=hello world'

encodeURIComponent(component: string): string

const param = 'hello world & goodbye';
const encoded = encodeURIComponent(param);
console.log(encoded);
// 'hello%20world%20%26%20goodbye'

// Build query string
const query = '?name=' + encodeURIComponent('John Doe') +
              '&email=' + encodeURIComponent('john@example.com');
console.log(query);
// '?name=John%20Doe&email=john%40example.com'

decodeURIComponent(encodedComponent: string): string

const encoded = 'hello%20world%20%26%20goodbye';
const decoded = decodeURIComponent(encoded);
console.log(decoded);
// 'hello world & goodbye'

// Parse query string
const queryString = 'name=John%20Doe&email=john%40example.com';
const parts = queryString.split('&');
const params = {};
for (const part of parts) {
  const [key, value] = part.split('=');
  params[decodeURIComponent(key)] = decodeURIComponent(value);
}
console.log(params);
// { name: 'John Doe', email: 'john@example.com' }

console.log(Infinity);           // Infinity
console.log(-Infinity);          // -Infinity
console.log(1 / 0);              // Infinity
console.log(-1 / 0);             // -Infinity
console.log(Infinity > 1000000); // true

console.log(NaN);                // NaN
console.log(0 / 0);              // NaN
console.log(Math.sqrt(-1));      // NaN
console.log(NaN === NaN);        // false (NaN is not equal to itself)
console.log(Number.isNaN(NaN));  // true

let x;
console.log(x);                  // undefined
console.log(typeof undefined);   // 'undefined'
console.log(undefined == null);  // true
console.log(undefined === null); // false

function convertToNumber(value) {
  const num = Number(value);
  
  if (isNaN(num)) {
    throw new TypeError('Cannot convert to number');
  }
  
  if (!isFinite(num)) {
    throw new RangeError('Number must be finite');
  }
  
  return num;
}

console.log(convertToNumber('42'));      // 42
console.log(convertToNumber('3.14'));    // 3.14
// convertToNumber('hello');             // TypeError
// convertToNumber(Infinity);            // RangeError

function parseInteger(str, radix = 10) {
  if (radix < 2 || radix > 36) {
    throw new RangeError('Radix must be between 2 and 36');
  }
  
  const result = parseInt(str, radix);
  
  if (isNaN(result)) {
    throw new Error('Failed to parse integer');
  }
  
  return result;
}

console.log(parseInteger('42'));         // 42
console.log(parseInteger('1010', 2));    // 10
console.log(parseInteger('ff', 16));     // 255

function buildQueryString(params) {
  const pairs = [];
  
  for (const key in params) {
    const encodedKey = encodeURIComponent(key);
    const encodedValue = encodeURIComponent(params[key]);
    pairs.push(`${encodedKey}=${encodedValue}`);
  }
  
  return pairs.join('&');
}

function parseQueryString(query) {
  const params = {};
  const pairs = query.split('&');
  
  for (const pair of pairs) {
    const [key, value] = pair.split('=');
    params[decodeURIComponent(key)] = decodeURIComponent(value);
  }
  
  return params;
}

const params = { name: 'John Doe', email: 'john@example.com' };
const query = buildQueryString(params);
console.log(query);
// 'name=John%20Doe&email=john%40example.com'

const parsed = parseQueryString(query);
console.log(parsed);
// { name: 'John Doe', email: 'john@example.com' }