A closure is a function value created from a possibly nested function declaration or function expression (i.e. lambda expression) whose body contains may one or more references to variables declared in an outer scope.
And here comes the closure part: The closure of a lambda expression is this particular set of symbols defined in the outer context (environment) that give values to the free symbols in this expression, making them non-free anymore.
But I honestly like the Closure + Closure::fromCallable approach, because string or array as callable has always been weird. Will B. Over a year ago @RoboRobok one reason for requiring only Closure (anonymous function) as opposed to callable, would be to prevent access beyond the scope of the called function.
A closure can actually be any function within another function, and its key characteristic is that it has access to the scope of the parent function including it's variables and methods.
A trailing closure is written after the function call’s parentheses, even though it is still an argument to the function. When you use the trailing closure syntax, you don’t write the argument label for the closure as part of the function call.
A closure is a pairing of: A function and A reference to that function's outer scope (lexical environment) A lexical environment is part of every execution context (stack frame) and is a map between identifiers (i.e. local variable names) and values. Every function in JavaScript maintains a reference to its outer lexical environment. This reference is used to configure the execution context ...
That's the magic, and frustration, of closure. "JavaScript Functions close over the scope they are declared in, and retain access to that scope even as variable values inside of that scope change." Using let instead of var solves this by creating a new scope each time the for loop runs, creating a separated scope for each function to close over.
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 ...
