calc-steps.txt

Calculator Application
Step-1 Generate Calculator Project and run it
npx create-react-app calcapp
cd calcapp
npm start

Step-2 Identify the components and build pages and components folder
And place the appropriate components inside the folders.

Components can be Button, Output and CalculatorPage Component

Step-3 Developing the component
Button Component contains the HTML Button , and click event attach
Output Component also contains the event so user can type and it can take expression 
If u identify all the buttons just do direct printing on output component, except = button , it do calculation before printing.
Note: printing (re-rendering) only when state change.

Step-4 Component need to communicate each other.
In our case Button click share the data to the output component.
Note : Data share using props only.

Step-5 Calculation 
Hint : you can use eval function of JS to evaluate the math expression
Once expression is eval then re-render it.