Higher order function returns pure function
Here's an example of an higher order function called functionA that has customValue as input and returns a function that gets an input and uses the custom value to elaborate a result: let functionA = (customValue) => { let value = customValue || 1; return input => input * value; }; Here's some results: functionA()(4) // => returns 4 functionA(2)(4) // => returns 8 functionA(3)(4) // => returns 12 functionA(4)(4) // => returns 16 Can the function returned by functionA be considered pure? UPDATE: the examples above are only using numeric input. As described by @CRice, the returned function can be considered pure only when customValue is constant and doesn't have internal state (like classes). Using this definition of Pure Function: In computer programming, a pure function is a function that has the following properties: Its return value is the same for the same arguments (no variation with local static variables, non-local va...