In this section we explain a number of common error codes that users experience in the real world.
Cannot find name gaCannot find name $Cannot find module jquery
You are probably using a third party library (e.g. google analytics) and don't have it declared. TypeScript tries to save you from spelling mistakes and using variables without declaring them so you need to be explicit on anything that is available at runtime because of you including some external library (more on how to fix it).