No, it does not matter the order you put the global variables or the functions (the order outside the functions). But it does matter the order inside a function.
A programming language is said to have First-class functions when functions in that language are treated like any other variable. For example, in such a language, a function can be passed as an argument to other functions, can be returned by another function and can be assigned as a value to a variable.
What is the difference between callback and higher-order function?
A higher-order function is a function that takes another function(s) as an argument(s) and/or returns a function to its callers. A callback function is a function that is passed to another function with the expectation that the other function will call it.
Memoization is an optimization technique that speeds up applications by storing the results of expensive function calls and returning the cached result when the same inputs occur again. …
Why is it called a callback function?
Simply put: A callback is a function that is to be executed after another function has finished executing — hence the name ‘call back’. … Because of this, functions can take functions as arguments, and can be returned by other functions. Functions that do this are called higher-order functions.
Do functions need to be in order?
Async callbacks are functions that are specified as arguments when calling a function which will start executing code in the background. When the background code finishes running, it calls the callback function to let you know the work is done, or to let you know that something of interest has happened.