Arithmetic Operations

JavaScript allows us to perform basic arithmetic operations. For instance, we can add using + and subtract using - like so:

let a = b + c - d;

To multiply, we use *, and for division, we use /:

let a = b * (c / d);

To find the remainder of a division, we can use %:

let x = 100 % 48;

Additionally, we can increment a variable with ++:

a++;

And decrement with --:

b--;

Type Checking

To determine the type of primitive values and objects, we use the typeof operator:

typeof a

This is particularly useful for primitive values, as it returns 'object' for all objects.

Assignment Operations

We assign a value to a variable using =:

let x = 10;

The value on the right is stored in the variable on the left. For instance, a += b is a shorthand for a = a + b, and we can also use -, *, and / in a similar fashion.

Comparison Operators

Equality is checked using ===:

a === b

To check for inequality, we use !==:

a !== b

We can determine if a is greater than b with:

a > b

And if a is less than b with:

a < b

For less than or equal to, we use:

a <= b

And for greater than or equal to:

a >= b

Logical operators include AND (&&):

a && b

And OR (||):

a || b

Date Manipulation in JavaScript

We can create date objects using the Date constructor:

let d = new Date("2017-06-23");

If we skip the month and day, it defaults to January 1:

let d = new Date("2017");

You can also specify hours, minutes, and seconds as follows:

let d = new Date("2017-06-23T12:00:00-09:45");

For a more human-readable format, you can use:

let d1 = new Date("June 23 2017");

let d2 = new Date("Jun 23 2017 07:45:00 GMT+0100 (Tokyo Time)");

Date objects come with various methods to retrieve specific values:

let d = new Date();

let a = d.getDay(); // Gets the day of the week

let b = d.getDate(); // Gets the day of the month

let c = d.getFullYear(); // Gets the full year

let h = d.getHours(); // Gets the hours

let ms = d.getMilliseconds(); // Gets the milliseconds

let m = d.getMinutes(); // Gets the minutes

let mo = d.getMonth(); // Gets the month

let s = d.getSeconds(); // Gets the seconds

let t = d.getTime(); // Gets milliseconds since 1970-01-01

We can also set values using setter methods:

let d = new Date();

d.setDate(d.getDate() + 7); // Sets the date to one week later

The setter methods include:

• setDay(): Sets the day of the week
• setDate(): Sets the day of the month
• setFullYear(): Sets the full year
• setHours(): Sets the hours
• setMilliseconds(): Sets the milliseconds
• setMinutes(): Sets the minutes
• setMonth(): Sets the month
• setSeconds(): Sets the seconds
• setTime(): Sets the timestamp