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Declaring a variable (with the keyword var) in the global scope (i.e. outside of any function body (or block in the case of let/const)), assigning a never declared identifier or adding a property to the global object (usually window) will also create a new global variable. Note that JavaScript's strict mode forbids the assignment of an ...
In compiled languages, global variables are generally static variables, whose extent (lifetime) is the entire runtime of the program, though in interpreted languages (including command-line interpreters), global variables are generally dynamically allocated when declared, since they are not known ahead of time.
Note that each call takes an extra argument, and two values are now returned; the ordinary return value, and a new value representing the state of the formerly mutable variable. Store-passing style can be quite painful to write, but can help to eliminate race conditions by isolating state within function calls, and can potentially make code ...
Non-local variables are the primary reason it is difficult to support nested, anonymous, higher-order and thereby first-class functions in a programming language. If the nested function or functions are (mutually) recursive, it becomes hard for the compiler to know exactly where on the call stack the non-local variable was allocated, as the frame pointer only points to the local variable of ...
Immediately invoked function expressions can be used to avoid variable hoisting from within blocks, protecting against polluting the global environment and simultaneously allowing public access to methods while retaining privacy for variables defined within the function. In other words, it wraps functions and variables, keeping them out of the ...
In computer programming, variable shadowing occurs when a variable declared within a certain scope (decision block, method, or inner class) has the same name as a variable declared in an outer scope. At the level of identifiers (names, rather than variables), this is known as name masking .
We can classify variables based on their lifetime. The different types of variables are static, stack-dynamic, explicit heap-dynamic, and implicit heap-dynamic. A static variable is also known as global variable, it is bound to a memory cell before execution begins and remains to the same memory cell until termination. A typical example is the ...
The term closure is often used as a synonym for anonymous function, though strictly, an anonymous function is a function literal without a name, while a closure is an instance of a function, a value, whose non-local variables have been bound either to values or to storage locations (depending on the language; see the lexical environment section below).