Is Javascript a Functional Programming Language?

Question

Just because functions are first class objects, there are closures, and higher order functions, does Javascript deserve to be called a Functional Programming language? The

Answer 1

What I really hate in javascript (if You try to look at it as FP language) is this:

function getTenFunctionsBad() {
  var result = [];
  for (var i = 0; i < 10; ++i) {
    result.push(function () {
      return i;
    });
  }
  return result;
}

function getTenFunctions() {
  var result = [];
  for (var i = 0; i < 10; ++i) {
    result.push((function (i) {
      return function () {
        return i;
      }
    })(i));
  }
  return result;
}

var functionsBad = getTenFunctionsBad();
var functions = getTenFunctions()
for (var i = 0; i < 10; ++i) {
  // using rhino print
  print(functionsBad[i]() + ', ' + functions[i]());
}

// Output:
//   10, 0
//   10, 1
//   10, 2
//   10, 3
//   10, 4
//   10, 5
//   10, 6
//   10, 7
//   10, 8
//   10, 9

You need to understand JS stack environment (I don't if it is the right term) to understand such a behavior.

In scheme for example You just can't produce such thing (Ok, ok -- with the help of underlying languages' references You can make it):

(define (make-ten-functions)
  (define (iter i)
    (cond ((> i 9) '())
          (else (cons (lambda () i) (iter (+ i 1))))))
  (iter 0))

(for-each (lambda (f)
            (display (f))
            (newline)) (make-ten-functions))