Add basic functions

script.js

@@ -0,0 +1,25 @@
+function Calculator(str) {
+
+    this.methods = {
+        "-": (a, b) => (a - b),
+        "+": (a, b) => (a + b), 
+        "/": (a, b) => (a / b),
+        "*": (a, b) => (a * b)
+    };
+
+    this.calculate = function(str) {
+        let parts = str.split(" ");
+        a = +parts[0];
+        op = parts[1];
+        b = +parts[2];
+
+        if (isNaN(a) || isNaN(b)) {
+            return NaN;
+        }
+        if (!this.methods[op]) {
+            return "Operation not supported."
+        }
+
+        return this.methods[op](a, b);
+    };
+}