var selection = [];

$(document).ready(function () {
    $(".calc-button").on("click", function () {
        var curr = $(this).text();
        if (curr !== "AC" && curr !== "=" && curr !== "DEL") {
            selection.push(curr);
            updateScreen();
        } else if (curr === "AC") {
            selection = [];
            $("#screen").text("0");
        } else if (curr === "DEL") {
            selection.pop();
            if (selection.length === 0) {
                $("#screen").text("0");
            } else {
                updateScreen();
            }
        } else if (curr === "=") {
            showAnswer();
        }
    });
});

function updateScreen() {
    $("#screen").text(selection.join(""));
}

function showAnswer() {
    selection = selection.map(function (curr, index) {
        if (curr === "÷") {
            return "/";
        } else if (curr === "×") {
            return "*";
        } else {
            return curr;
        }
    });
    var answer;
    try {
        answer = eval(selection.join(""));
    } catch (e) {
        if (e instanceof SyntaxError) {
            answer = "Math error";
        }
    }
    selection = [];
    answer = (answer + "").replace("Infinity", "∞");
    answer = (answer + "").replace("NaN", "Error 404, logic not found");
    $("#screen").text(answer);
}