Javascript: Add keyboard input to calculator

Question

Started a little project yesterday to make a calculator. I think it's fully working but I want to go a step further and add keyboard input (like you can on factory default OS calculators)

I have found an answer on here but it was for C#.

So:

How in JavaScript can I add keyboard input? This would include 0-9, all operators, "C" to clear and "delete"/"esc" to remove last entry.

Ideally I would like the css hover effect (darker shade) I did to happen
when clicking on the key too.

You can view the start here: http://codepen.io/apswak/pen/RapEqp

index.html

<div id="calculator">
  <div id="screen">
    <div id="calc">0</div>
    <div id="result">0</div>
  </div>
  <button class="value">1</button><button class="value">2</button><button class="value">3</button><button class="value">+</button><button class="value">4</button><button class="value">5</button><button class="value">6</button><button class="value">-</button><button class="value">7</button><button class="value">8</button><button class="value">9</button><button class="value">*</button><button class="value">.</button><button class="value">0</button><button class="CE">   &larr;</button><button class="value">/</button><button class="equals">=</button><button class="C">C</button>

</div>

script.js

$(document).ready(function() {

  var string = "";

  /* Calculator input string */
  $(".value").click(function() {
    string += $(this).text();
    $("#calc").text(string);
  });

  /* Clear all */
  $(".C").click(function() {
    string = "";
    $("#calc, #result").text("0");
  });
  /* Clear last entry */
  $(".CE").click(function() {
    string = string.slice(0, string.length - 1);
    $("#calc").text(string);
  });

  /* Show result */
  $(".equals").click(function() {
    $("#result").text(eval(string));
  });

});

Answer 1

Here's an example with keypress function on your codePen example :

http://codepen.io/anon/pen/WwjNao

   document.onkeypress = function (e) {
        keyPressed = String.fromCharCode(e.which);        
        if($("#calc").length > 0){
          $("#calc").append(keyPressed);
        }else{
          $("#calc").text(keyPressed);
        }
    };

It's an hint, I will not give you all the code ;)

Answer 2

I've started you off with some basic numbers in a copy of your code pen

You have to listen for a keypress and match the key (event.which) to the event it should trigger.

$(document).keypress(function(event){
    console.log(event.which);
    //0
    if(event.which == 48){
      string += 0;
      $("#calc").text(string);
    }
});

http://codepen.io/anon/pen/LNyYJM

Also if you do 0123+5 it says it equals 88 so you may want to make note of that as a bug.

Answer 3

You could use keypress https://api.jquery.com/keypress/ and listen to which key is being pressed.

Keycodes:https://css-tricks.com/snippets/javascript/javascript-keycodes/

$( "#target" ).keypress(function( event ) {
    if ( event.which == 48 ) {
    // Return #0
}
if ( event.which == 49 ) {
    // Return #1
}
// and so on...
});