calculator.js

export const CalcMachine = () => {
    let state = '';

    const operators = ['+', '-', '*', '/'];
    const sumReducer = (acc, value) => acc + value;
    const mulReducer = (acc, value) => acc * value;
    const divReducer = (acc, value) => acc / value;
    const subReducer = (acc, value) => acc - value;

    const sum = (args) => args.reduce(sumReducer);
    const mul = (args) => args.reduce(mulReducer);
    const div = (args) => args.reduce(divReducer);
    const sub = (args) => args.reduce(subReducer);

    const calcDict = { '+': sum, '-': sub, '*': mul, '/': div };

    const parseOperator = (value) => operators.find(op => value.includes(op));

    const calculate = (operator) => {
        if (operator) {
            const arr = state.split(operator).map(el => parseInt(el));

            return calcDict[operator](arr);
        }
    }

    const push = (value) => {
        let existOperator = parseOperator(state);
        let newOperator = parseOperator(value);
        if (existOperator && newOperator) {
            state = calculate(existOperator)
        }

        state += value;

        return state;
    }

    const reset = () => {
        state = '';

        return state;
    }

    const parseAndCalculate = () => {
        const operator = parseOperator(state);
        state = calculate(operator);

        return state;
    }

    return { push, reset, parseAndCalculate }
}