Regex Solution to Server Side Calculator

server-side-calculator-regex.js

// Track the equation as a string
let equation = '';

// 🤯 🤯 🤯 🤯 🤯 🤯 🤯 
// This regular expression defines a set of "rules" for 
// how our equation string should look
// It also tells us how to break apart the different sections of the
// string into "groups"
// These are super powerful, though not always so easy to use 😉
let equationRegEx = /^([0-9]+(\.[0-9]+)?)?([\+\-\/\*])?([0-9]+(\.[0-9]+)?)?$/

function onInput() {
    // Add the clicked button to the equation string
    let nextEquation = equation += $(this).text();

    // Parse the equation string into "groups"
    let matches = nextEquation.match(equationRegEx);

    // If the equation does not match our regular expression, 
    // show an error
    if (!matches) {
        alert('Invalid equation!');
        return;
    }

    // Grab each matching "group" from the equation
    // to get our parsed equation object
    let submission = {
        firstNum: Number(matches[1]),
        operator: matches[3],
        secondNum: Number(matches[2]),
    }

    // etc...
}