javascript - Intercept input entering -

is there way intercept value user inputs before ever appears in element? tried use object.defineproperty appears not work inputelement.value since

var value; object.defineproperty($('input')[0], 'value', {     get: function() {return value},     set: function(val) {console.log(val); value = val;} }); 

doesn't appear change behavior. or oninput/onchange option? since i'd rather have code executes before browser's.

http://jsfiddle.net/zpmu1xcu/

if want detect input before text entered browser, can use element.onkeydown property. event fires key pressed down, before browser interprets action.

var demo_i = document.getelementbyid('demo_i');  var demo_d = document.getelementbyid('demo_d');    demo_i.onkeydown = function(e) {      demo_d.textcontent = e.which;      // returning false stops event going further      return false;  }

<input id="demo_i"><div id="demo_d"></div>