Javascript That Works - Throwing Errors & Failing?

Javascript errors tend to mess up projects easily. Debug and test continuously. A single typo can mess up everything...   A javascript error not perse needs to make your complete course not working... depends somewhat on the type of error. If a variable mismatches and its not used in critical processes the course may run normally with only returning null or undefined for that variable. If in your code returning null or undefined is managed properly eg. an if statement or case switch that makes sure the code wont stop and sets the variable to a default... then  your projects flow will be uninterrupted.