JavaScript built-in objects

specialized objects (the "jargon sets")

Sometimes we need specialized objects to help express what we want to do - a specialized "vocabulary" within the programming language (a jargon!) ...

... behold, some examples of built-in objects:

Date

JavaScript comes with a built-in Date object which tells us the current date but in its standard format

const today = new Date()
// Sat Feb 20 2021 10:00:00 GMT -0500 (Eastern Standard Time)

There exist many ways to format this date via other functions (as well as writing our own) which we can read in the Mozilla Developer docs!

Math

JavaScript comes with a built-in Math object that allows us to do essential mathematical functions without having to rewrite them, e.g.:

// this gives us a random decimal between 0 and 1
const randomNumber = Math.random() 

// we can multiply that by 100
const someNumber = 100 * randomNumber()

// this would round up the previous random number
const someInteger = Math.floor(someNumber) 

// this would round down
const someIntegerRoundedDown = Math.ceil(someNumber)

We can call other functions of Math such as:

• Math.sin(x) to get "the sine of x"

• Math.sqrt(x) to get "the square root of x"

• Math.pow(x, y) to get "x to the power of y"

We can also use its properties such as:

• Math.PI to get an approximation of pi (3.14159)

• Math.E to get an approximation of Euler's constant (2.718)

References

• See Date and Math as well as Global Objects in the Mozilla Developer Docs