AngularJS directive input width resize by keyup

Question

I created a directive in order to make a input that has width automatically resized when keyup (like Google Contacts). However it seems not to be ok, because the width of each characters is different. Could you please help me to give a more optimized way? Tks.

http://plnkr.co/edit/DSn0JDDShOXvuXXF9PP2?p=preview

Answer 1

Based on @notme's answer I created the following gist for my own version of an auto-resizing input angular directive:

https://gist.github.com/Zmaster/6923413

Here is the code:

Template:

<span>
  <input type="text" ng-model="value">
  <span style="visibility:hidden; position:absolute; left:-1000; top:-1000;">{{value}}</span>
</span>

Directive:

angular.module('autoSizeInput', []) 
  .directive('autoSizeInput', function() {
    return {
      replace: true,
      scope: {
        value: '=inputValue'
      },  
      templateUrl: 'templates/directives/autoSizeInput.html',
      link: function(scope, element, attrs) {
        var elInput = element.find('input');
        var elSpan = element.find('span');
        elSpan.html(elInput.val());

        scope.$watch('value', function(value) {
          if(value) {
            elSpan.html(elInput.val());
            elInput.css('width', (elSpan[0].offsetWidth + 10) + 'px');
          }   
        }); 
      }   
    };  
  });