Build your first SPFx client-side Hello World web part

In the series of SPFx tutorials, we are going to learn how we can create our first SPFx webpart step by step.

Create a folder in your local machine either using file explorer or command prompt.
In my case, I have created a folder named helloworld-webpart in my C drive
To create a folder using command promt, run below command
```
md helloworld-webpart
```
Once the folder is created, navigate to the folder by using below command
```
cd helloworld-webpart
```

Yeoman SharePoint generator used to scafold your SPFx webpart. Scafolding means, generating a folder structure that contains necessaory files and folders to start with SPFx webpart.
Create a new HelloWorld web part by running the Yeoman SharePoint Generator
```
yo @microsoft/sharepoint
```
You will be promted to enter some information related to your webpart as below
a) What is your solution name? Hit enter to keep the default name which is hellowworld-webpart
b) Which platform you need to use? Select SharePoint Online and hit enter
c) Use the current folder
d) Select N to allow the solution to be deployed to all sites immediately.
e) Select N on the question if solution contains unique permissions
f) Select Webpart component
g) Enter webpart name? Hit enter to keep the default
h) Enter description: hit enter to keep the default
i) Select framework: we will go with widely used framework which is React
Once the scaffolding is done, you will see a message as below

Developer certificate has to be installed ONLY once in your development environment, so you can skip this step if you have already executed that in your environment.
To install the developer certificate use below command
```
gulp trust-dev-cert
```

You can preview your webpart using below command
```
gulp serve
```
When we run this command, it will create a local, node-based HTTPS server on your machine.
Local workbench will open in your default browser and you can see a dummy SharePoint modern page where you can add a web part
Click on add button and select the hello world webpart

To preview the hello world web part, open the below link in your browser
https://yoursharepointsite.sharepoint.com/sites/testsite/_layouts/15/workbench.aspx