Programming with Mosh
In this 3-minute introduction , I ’m going to answer four frequently asked questions about JavaScript. Wha
t is JavaScript, what can you do with it, where does JavaScript code run and what is the difference betwe
en JavaScript and ECMAScript. The average salary of a JavaScript developer in the United States is $ 72
,000 a year. Every browser has a JavaScript engine and we can easily write JavaScript code here without
any additional tools of course this is not how we build real-world applications but this is just for a quick de
mo. In order to write javascript code you need a code editor there are various code editors out there inclu
ding Visual Studio code or yes code sublime text atom. Live server is a lightweight web server that we ’re
going to use to serve our web application so install this then you will have to restart Visual Studio code wh
en you ’re done go to the Explorer tab right click index. html and select open with live server. This will ope
n up Chrome or your default browser and point it to this address that’s where web application is served fro
m now.
JavaScript is a statement a statement is a piece of code that expresses an action to be carried out in this
case we want to log a message on the console. All statements in JavaScript should be terminated by a se
micolon. In JavaScript we can add some description to our code and this description is ignored by the Jav
aScript engine. In this lecture I ’m assuming that you have installed node on your machine if not head ove
r to node. js org and download the latest version of node. combine these files into a bundle and serve that
bundle to the client. Save the changes back in the browser you can still see the hello world message and
that confirms that our code is still working. A variable is one of the most fundamental concepts in JavaScr
ipt and any other programming languages in programming. We use a variable to store data temporarily in
a computer ’s memory. We store our data somewhere and give that memory location and name and with t
his name we can read the data at the given location in the future. The best practice is to use the lead key
word to declare a variable.
The modern best practice is to declare each variable on a single line so we terminate this first declaration
with a semicolon and declare the second variable on new line that ’s the modern best best practice next w
e ’re going to look at constants alright now let ’s declare a variable called interest rate so let interest rate a
nd we set this to 0. 3 now this is the initial value. The best practice is to use a constant so the value of a v
ariable as the name implies can change but a constant can not change so here if we change let to Const
now interest rate will be a constant. In situations where we want to have some logic for example if the ord
er is approved then it needs to be shipped. JavaScript is a dynamic language so unlike other programmin
g languages the type of these variables will be determined at runtime based on the values that we assign
ed to them. In JavaScript unlike other languages we don’t have two kinds of numbers we do n’t have floati
ng-point numbers and integers. In es6 we have another primitive that is symbol and you ’re going to learn
about that later in the course