How would you explain JavaScript closures to someone with a knowledge of the concepts they consist of (for example functions, variables and the like), but does not understand closures themselves? ...
But the callback function in the setTimeout is also a closure; it might be considered "a practical use" since you could access some other local variables from the callback. When I was learning about closures, realising this was useful to me - that closures are everywhere, not just in arcade JavaScript patterns.
3 Closures fit pretty well into an OO world. As an example, consider C# 3.0: It has closures and many other functional aspects, but is still a very object-oriented language. In my experience, the functional aspects of C# tend to stay within the implementation of class members, and not so much as part of the public API my objects end up exposing.
I frequently choose to use closures in the Strategy Pattern when the strategy is modified by data at run-time. In a language that allows anonymous block definition -- e.g., Ruby, C# -- closures can be used to implement (what amount to) novel new control structures. The lack of anonymous blocks is among the limitations of closures in Python.
Lambdas and closures are each a subset of all functions, but there is only an intersection between lambdas and closures, where the non-intersecting part of closures would be named functions that are closures and non-intersecting lamdas are self-contained functions with fully-bound variables.
A closure in C# takes the form of an in-line delegate/ anonymous method. A closure is attached to its parent method meaning that variables defined in parent's method body can be referenced from within the anonymous method. Example:
What do the closures capture exactly? Closures in Python use lexical scoping: they remember the name and scope of the closed-over variable where it is created. However, they are still late binding: the name is looked up when the code in the closure is used, not when the closure is created. Since all the functions in your example are created in the same scope and use the same variable name ...
A closure is a first class function with bound variables. Roughly that means that: You can pass the closure as a parameter to other functions The closure stores the value of some variables from the lexical scope that existed at the time that is was created Java initially didn't have syntactic support for closures (these were introduced in Java 8), although it was fairly common practice to ...
