Strict Null Checks
This lesson introduces the most important `strict` mode compiler flag - `strictNullChecks`. This flag can help you elevate the type safety of your code to a completely new level. It addresses the billion-dollar mistake of programming languages, null references.
The billion-dollar mistake
The expression comes from Thomas Hoare, a famous and influential computer scientist who introduced null references to ALGOL in 1965. Many years later he admitted that it was a mistake, as it resulted in “innumerable errors, vulnerabilities, and system crashes, which have probably caused a billion dollars of pain and damage in the last forty years.”
What does it mean in the context of JavaScript and TypeScript?
Uncaught TypeError: Cannot read property 'foo' of undefined
Are you familiar with this error message? I bet you are. It occurs whenever you’re trying to access a property or method of an object that you think is present, but turns out to not be there.
There are two ways of representing empty values in JavaScript - null and undefined. This kind of error can occur in both cases. ...