backup

js_workshop6/index.js

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+
+    // Creates the Calculator Object
+function Calculator() {
+    this.number1 = 0;
+    this.number2 = 0;
+    this.op = 'add';
+    this.add = function() { return this.number1 + this.number2; }
+    this.minus = function() { return this.number1 - this.number2; }
+    this.multiply = function() { return this.number1 * this.number2; }
+    this.divide = function() { return this.number1 / this.number2; }
+    this.Calculate = function getResult() {
+        if (this.op === 'add') return this.add();
+        if (this.op === "mult") return this.multiply();
+        if (this.op === "minus") return this.minus();
+        if (this.op === "div") return this.divide()
+    }
+}
+
+// Create Event Listener for button
+document.getElementById('calculate').addEventListener('click', getResult, false);
+
+// Instantiate Calculator
+let calculator = new Calculator();
+
+// Validates input and sets disabled input box to result
+function getResult() {
+    // handler function for the calcButton
+    if (document.getElementById("num1").value === "") {
+        // show error or make a page element show the error
+        alert("Enter some values")
+        return;
+    }
+    // Give object variables values.
+    calculator.number1 = parseFloat(document.getElementById("num1").value);
+    calculator.number2 = parseFloat(document.getElementById("num2").value);
+    calculator.op = document.getElementById("operator").value;
+    // This is pretty cool, + typecasts to Number, I multiply by 100, then divide by 100,
+    // while avoiding rounding errors!
+    document.getElementById('result').value = +(Math.round(calculator.Calculate() + "e+2") + "e-2");
+}