calculator.js

var validResults = [];
var total = 0;

document.write("<table>");
document.write("<tr><th>Number 1</th><th>Operator</th><th>Number 2</th><th>Result</th></tr>");

while (true) {

    var x = prompt("Enter first number (Cancel to stop):");
    if (x === null) break;

    var operator = prompt("Enter operator (+, -, *, /, %):");
    if (operator === null) break;

    var y = prompt("Enter second number:");
    if (y === null) break;

    var result;

    if (isNaN(x) || isNaN(y)) {
        result = "Wrong input number";
    } else {
        x = Number(x);
        y = Number(y);

        if (operator === "+") {
            result = x + y;
        } else if (operator === "-") {
            result = x - y;
        } else if (operator === "*") {
            result = x * y;
        } else if (operator === "/") {
            result = y !== 0 ? x / y : "Division by zero error";
        } else if (operator === "%") {
            result = y !== 0 ? x % y : "Division by zero error";
        } else {
            result = "Computation error";
        }

        if (typeof result === "number") {
            validResults.push(result);
            total += result;
        }
    }

    document.write("<tr><td>" + x + "</td><td>" + operator + "</td><td>" + y + "</td><td>" + result + "</td></tr>");
}

document.write("</table>");

if (validResults.length > 0) {

    var min = validResults[0];
    var max = validResults[0];

    for (var i = 1; i < validResults.length; i++) {
        if (validResults[i] < min) min = validResults[i];
        if (validResults[i] > max) max = validResults[i];
    }

    var avg = total / validResults.length;

    document.write("<h3>Summary</h3>");
    document.write("<table>");
    document.write("<tr><th>Minimum</th><th>Maximum</th><th>Average</th><th>Total</th></tr>");
    document.write("<tr><td>" + min + "</td><td>" + max + "</td><td>" + avg + "</td><td>" + total + "</td></tr>");
    document.write("</table>");
}