What is the purpose of the following function in this code block?

Question

I can't seem to figure out what the actual importance is for including the following block of code in an exercise in Chapter 6 of Eloquent Javascript.

Edit: It's not needed but rather there to allow for calling it from the top level.

function countZeroes(array) {
  return count(equals(0), array);
}

Here is the full code:

function count(test, array) {
  return reduce(function(total, element) {
    return total + (test(element) ? 1 : 0);
  }, 0, array);
}

function equals(x) {
  return function(element) {return x === element;};
}

function countZeroes(array) {
  return count(equals(0), array);
}

Here is the reduce function from earlier:

function reduce(combine, base, array) {
  forEach(array, function (element) {
    base = combine(base, element);
  });
  return base;
}

Here is the forEach function from earlier:

function forEach(array, action) {
  for (var i = 0; i < array.length; i++)
    action(array[i]);
}

I've only just begun learning JavaScript so I'm sure there is a simple explanation for this. Thanks.

Answer 1

The method is never called...

Most probably the intention is to be able to call it from the top level. Instead of:

show(count(equals(0), [2, 4, 5, 0, 3, 0, 0, 3]));

you could have

var a = [1,4,5,0];
show( countZeroes( a ) );

Answer 2

Because the function countZeros never called.

I think the native function Array.filter is better/faster.

function count (whatToCount, theArrayToCount) {
    return theArrayToCount.filter (function (element) {
        // If they are same, keep; Otherwise remove from array
        return element === whatToCount;
    }).length; // Count the "filtered" Array, and return it.
}

count (0, [2, 4, 5, 0, 3, 0, 0, 3]); // 3

btw, the callbacks are confusing (..