solution for excel app

excel.js

function polishPostfix(str) {
    let arr = str.split(' ');
    let st = [];
    for (let item of arr) {
        // console.log(st, item);
        let a;
        switch (item) {
            case '+':
                st.push(st.pop() * 1 + st.pop() * 1);
                break;
            case '-':
                a = st.pop();
                st.push(st.pop() - a);
                break;
            case '*':
                st.push(st.pop() * st.pop());
                break;
            case '/':
                a = st.pop();
                st.push(st.pop() / a);
                break;
            default:
                st.push(item);
                break;
        }
    }
    return st.pop();
}
function deRef(key, str, obj, tmp = []) {
    // console.log(str);
    if (!isNaN(str)) {
        return str
    }
    let arr = str.split(' ');
    let len = arr.length;
    let ar2 = [];
    for (let i = 0; i < len; i++) {
        let item = arr[i];
        if (['+', '-', '*', '/'].includes(item) || !isNaN(item)) {
            ar2.push(item);
        } else {
            if (key === item) {
                throw `Circular dependency between ${key} and ${tmp[0]} detected`;
            }
            tmp.push(item);
            ar2.push(deRef(key, obj[item], obj, tmp));
        }
    }
    return ar2.join(' ');
}

function excel(n, obj) {
    try {
        let keys = Object.keys(obj);
        for (let key of keys) {
            let value = obj[key];
            if (isNaN(value)) {//string
                obj[key] = polishPostfix(deRef(key, value, obj));
            }
        }
        for (let key of keys){
            console.log(key);
            console.log(obj[key]);
        }
    } catch (e) {
        console.log(e);
        
    }
}

excel(3, {
    A1: 5,
    A2: 'A1 5 * B1 +',
    B1: 6
});
console.log('---------------');
excel(3, {
    A1: 5,
    A2: 'A1 5 * B2 +',
    B1: 6,
    B2: 'B1 C1 /',
    C1: 2
});

console.log('---------------');
excel(2, {
    A1: 'A2 2 *',
    A2: 'A1 5 +'
});


console.log('---------------');
excel(4, {
    A1: 'B2 2 *',
    A2: 'B1 5 +',
    B1: 'B2 2 +',
    B2: 'A1 1 *'
});