Basic JavaScript Calculator

Photo by Amol Tyagi on Unsplash

This week, I thought I’d challenge myself to implement a simple calculator. I started off with a string input consisting of two numbers and the basic operations (+, -, *, /).

I immediately thought, I could proceed with a switch statement, and came up with my function.

function calculator(string) {
    let calculation = string.split(/\b\s*([+\/*-])\s*/)
    const expression = calculation[1]
    switch(expression) {
        case "*":
            return parseInt(calculation[0])*parseInt(calculation[2])
            break;
        case "/":
            return parseInt(calculation[0])/parseInt(calculation[2])
            break;
        case "+":
            return parseInt(calculation[0])+parseInt(calculation[2])
            break;
        case "-":
            return parseInt(calculation[0])-parseInt(calculation[2])
            break;
        default:
            return (`Error ${string} contains an invalid operation.`)
    }
}

Voila! Functional.

I wanted to shift focus to the second line of the code, which was provided through Stack Overflow.

let calculation = string.split(/\b\s*([+\/*-])\s*/)

When I first tried splitting by operation, I quickly saw several edge cases that were not being covered. Thankfully, I came across the code above with a quick Google search. This line uses Regular Expression to elegantly split the string input, ignoring periods, and including negatives in order to get an accurate and hassle-free result.

Now that we have the basic calculator down, how would you support the order of operations in a more advanced calculator?