Create keys.js

This file allow the calculator to be used pressing the keyboard

keys.js

@@ -0,0 +1,79 @@
+window.onkeydown = function(e) {
+if (e.keyCode == 8 && e.target == document.body || e.keyCode == 111 && e.target == document.body) 
+    e.preventDefault(); //disable the turn back page function of backspace and / search page function
+}
+
+document.addEventListener('keydown', function(event) {
+    if(event.keyCode == 97 || event.keyCode == 49 ) {
+        display.value += '1';
+    }
+
+    if(event.keyCode == 98 || event.keyCode == 50 ) {
+        display.value += '2';
+    }
+
+    if(event.keyCode == 99 || event.keyCode == 51 ) {
+        display.value += '3';
+    }
+
+    if(event.keyCode == 100 || event.keyCode == 52 ) {
+        display.value += '4';
+    }
+
+    if(event.keyCode == 101 || event.keyCode == 53 ) {
+        display.value += '5';
+    }
+
+    if(event.keyCode == 102 || event.keyCode == 54 ) {
+        display.value += '6';
+    }
+
+    if(event.keyCode == 103 || event.keyCode == 55 ) {
+        display.value += '7';
+    }
+
+    if(event.keyCode == 104 || event.keyCode == 56 ) {
+        display.value += '8';
+    }
+
+    if(event.keyCode == 105 || event.keyCode == 57 ) {
+        display.value += '9';
+    }
+
+    if(event.keyCode == 96 || event.keyCode == 48 ) {
+    display.value += '0';
+    }
+
+    if(event.keyCode == 70 ) {
+    alert("You Pay Respect! Thanks <3 ");
+    }
+
+    if(event.keyCode == 107 ) {
+    display.value += '+';
+    }
+
+    if(event.keyCode == 109 ) {
+    display.value += '-';
+    }
+
+    if(event.keyCode == 106 ) {
+    display.value += '*';
+    }
+
+    if(event.keyCode == 111 ) {
+    display.value += '/';
+    }
+
+    if(event.keyCode == 8 ) {
+        display.value = display.value.slice(0,-1);
+        }
+
+    if(event.keyCode == 67 || event.keyCode == 46 ) {  // C and Del can erase the Calculator
+    display.value = '';
+    }
+
+    if(event.keyCode == 13 ) {  // Enter key can show the result of the math exp.
+        display.value = eval(display.value);
+    }
+
+});