1.think the origin of the type over and over. 2. consider if others have encountered a similar situation. 2.1 yes perhaps you can find answer from the forum or official site 2.2 no perhaps there was a stupid mistake made by you. 3. try to use Bisection Method to divide the source code This way can pinpoint the problem quickly. debug skills delete the half code recursively This is a very useful way. debug in frontend 1. must use dev tools. 2. try to override the original codes.