The Effect of Smartphone Application on the Quality of Bowel Preparation for Colonoscopy

The goal of this clinical trial is to learn about bowel preparation methods compared between standard techniques and enhanced education with application for elective colonoscopy. The main questions it aims to answer are: Which bowel preparation method results in an adequate bowel preparation rate? Participants will: * Random to 1:1 ratio to be educated via the smartphone application (APP group) or the standard education (control group). * Received the same purgative regimen and diet restriction. * Endoscopist-blinded colonoscopy the participants and give score of bowel preparation scale (use Boston Bowel Preparation Scale)