I had to build a calculator for the freeCodeCamp Frontend Frameworks track, so I chose to build it with React.

The fCC assignment notes:

There are two main schools of thought on calculator input logic: immediate execution logic and formula logic. Our example utilizes formula logic and observes order of operation precedence, immediate execution does not. Either is acceptable.

EXAMPLE: 3 + 5 x 6 - 2 / 4 =

• Immediate Execution Logic: 11.5
• Formula/Expression Logic: 32.5

• The calculator uses formula/expression logic, not immediate execution
• The calculator has four digits of decimal precision when dealing with fractions
• Numbers and operations are stored as separate equation parts in an array. It needs two passes to properly address order of operation precedence
• The calculator doesn't make use of eval or libraries
• There are no plans to add new features in the near future (e.g. square root, etc.)

• Simplicity is hard. Things that look simple disguise their complexity (especially when you're new to code)
• Avoiding eval and libraries is the path of most resistance, but also gave birth to some epic struggles. It's rare to find a tutorial that doesn't defer to eval. Some opinions say this is fine for a calculator app, but there's an argument for not learning a tool that you wouldn't want to use in many other contexts given its risks.
• DuckDuckGo's calculator is very cute.

Made with Create React App.