dynamic define image click on display error dialog in webos application

Question

hi

i am develop some service app i am display 3 columns cart image ,second one is lable ,third one quantity (edittext). click on cart button to validations occurs quantity is enter number? null this situation display error dialog how can implemented validation and error dialog

this.str = this.str+'<td><div id="imageclick"><img src="images/cartimage.png" onclick=""/></div></td>';//cart image
this.str = this.str+' <td>'+itemslist[i]+'</td>';//item lable
this.str = this.str+'<td><input type="text" size="5"></td>';//quantity