Nine Javascript Gotchas

Nine Javascript Gotchas
Realazy » JavaScript的9个陷阱及评点

<input type="button" value="Gotcha!" id="MyButton" >
<script>
var MyObject = function () {
    this.alertMessage = "Javascript rules";
    this.ClickHandler = function() {
          alert(this.alertMessage );
      }
}();
document.getElementById("theText").onclick =  MyObject.ClickHandler
</script>

If you call MyObject.OnClick(); you will get a popup saying "Javascript rules".
However, if you click on the button "MyButton", the popup will say "undefined"

<input type="button" value="Gotcha!" id="theText" >
<script>
var MyObject = function () {
    var self = this;
    this.alertMessage = "Javascript rules";
    this.OnClick = function() {
          alert(self.value);
      }
}();
document.getElementById("theText").onclick =  MyObject.OnClick
</script>