What is meant by ‘first class object’?

To quote Wikipedia:

In computer science, a programming
language is said to support
first-class functions (or function
literal) if it treats functions as
first-class objects. Specifically,
this means that the language supports
constructing new functions during the
execution of a program, storing them
in data structures, passing them as
arguments to other functions, and
returning them as the values of other

This page also illustrates it beautifully:

Really, just like any other variable

  • A function is an instance of the Object type
  • A function can have properties and has a link back to its constructor method
  • You can store the function in a variable
  • You can pass the function as a parameter to another function
  • You can return the function from a function

also read TrayMan’s comment, interesting…

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