jsGlobalObjects.md

Global Objects

Global Objects MDN Docs

Global Object Methods

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Date

The Date object is used to work with dates and times in JavaScript. It allows you to create, format, and manipulate dates and times.

const today = new Date();
console.log(today); // Mon Feb 13 2023 22:19:07 GMT+0530 (India Standard Time)

//Example:
const birthdate = new Date('June 25, 1998');
console.log(birthdate.toDateString()); // Mon Jun 25 1998

Error

The Error object is a built-in object in JavaScript that represents an error. It is thrown when a runtime error occurs and can be caught using a try...catch statement.

try {
  // Code that might throw an error
} catch (error) {
  console.error(error);
}

//Example:
try {
  throw new Error('An error occurred');
} catch (error) {
  console.error(error); // Error: An error occurred
}

JSON

The JSON object is a built-in object in JavaScript that allows you to parse and stringify JSON data. JSON (JavaScript Object Notation) is a lightweight data-interchange format that is easy for humans to read and write and easy for machines to parse and generate.

const data = { name: 'John Doe' };
const json = JSON.stringify(data);
console.log(json); // {"name":"John Doe"}

const parsedData = JSON.parse(json);
console.log(parsedData); // { name: 'John Doe' }

//Example:
const response = '{"name":"John Doe","age":30}';
const user = JSON.parse(response);
console.log(user.name); // John Doe

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Set

The Set object is a built-in object in JavaScript that allows you to store unique values. It is similar to an array but does not allow duplicate values.

const items = new Set();
items.add(1);
items.add(2);
items.add(3);
console.log(items.size); // 3
console.log(items.has(2)); // true

//Example:
const names = new Set(['John', 'Jane', 'Jim']);
console.log(names.size); // 3
names.delete('Jane');
console.log(names.size); // 2

Symbol

The Symbol object is a built-in object in JavaScript that allows you to create unique and immutable symbols. They are used as property keys and can be used to create private properties.

const symbol = Symbol();
console.log(typeof symbol); // symbol

//Example:
const age = Symbol();
const user = { name: 'John Doe' };
user[age] = 30;
console.log(user[age]); // 30

Map

The Map object is a simple key/value map. Any value (both objects and primitive values) may be used as either a key or a value.

const map = new Map();
map.set('key1', 'value1');
map.set('key2', 'value2');
console.log(map.get('key1')); // Output: value1

//Example:
const map = new Map();
map.set('name', 'John');
map.set('age', 30);
console.log(map.get('name')); // Output: John
console.log(map.get('age')); // Output: 30

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WeakMap

The WeakMap object is a collection of key/value pairs in which the keys are objects and the values can be arbitrary values. The keys are held weakly, which means that they do not prevent garbage collection in case there is no other reference to the object.

const weakMap = new WeakMap();
const obj = {};
weakMap.set(obj, 'value');
console.log(weakMap.get(obj)); // Output: value

//Example:
const weakMap = new WeakMap();
const obj = {};
weakMap.set(obj, {name: 'John'});
console.log(weakMap.get(obj)); // Output: {name: 'John'}

WeakSet

The WeakSet object is a collection of objects (it does not accept any primitive value types). The objects in the WeakSet are held weakly, which means they do not prevent garbage collection in case there is no other reference to the object.

const weakSet = new WeakSet();
const obj = {};
weakSet.add(obj);
console.log(weakSet.has(obj)); // Output: true

//Example:
const weakSet = new WeakSet();
const obj1 = {};
const obj2 = {};
weakSet.add(obj1);
weakSet.add(obj2);
console.log(weakSet.has(obj1)); // Output: true
console.log(weakSet.has(obj2)); // Output: true

Promise

The Promise object is used for asynchronous computations. A Promise represents a value that may not be available yet, but will be at some point in the future.

const promise = new Promise((resolve, reject) => {
  setTimeout(() => {
    resolve('Success');
  }, 1000);
});

promise.then((value) => {
  console.log(value); // Output: Success
});

//Example:
const promise = new Promise((resolve, reject) => {
  setTimeout(() => {
    resolve('Data Loaded');
  }, 2000);
});

promise.then((value) => {
  console.log(value); // Output: Data Loaded
});

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parseInt

parseInt() is a built-in function in JavaScript that parses a string argument and returns an integer of the specified radix (the base in mathematical numeral systems).

const integer = parseInt(string, radix);

//Example:
const age = parseInt("27", 10);
console.log(age); // 27

const hex = parseInt("FF", 16);
console.log(hex); // 255

parseFloat

parseFloat() is a built-in function in JavaScript that parses a string argument and returns a floating-point number.

const float = parseFloat(string);

//Example:
const height = parseFloat("6.2");
console.log(height); // 6.2

const weight = parseFloat("180.5 lbs");
console.log(weight); // 180.5