Modern Front-End Development for Rails

Chapter 6TypeScript

In programming, the type of a piece of variable data indicates the set of values that are valid for that data. For example, if I say that a variable is an integer, that means I expect the variable to have a value like 1, -3, or 357 and not a value like banana. If the variable is set to a value that is not of the expected type, we think that something bad will happen. In some languages, the attempt to set data to the wrong value leads to a compiler error; in other languages it leads to incorrect or unspecified behavior at run time.

All high-level programing languages use some concept of type to determine behavior. Which is to say that all of these languages determine behavior by using not just the value of a variable in the ...