Javascript递归-好像变量作用域使事情搞砸了

Question

I'm trying to improve my JS by creating a numbers-to-words function in javascript. Ie, it takes 1234 and spits out "one thousand two hundred thirty four". Coming from a Ruby background and wanting to write something recursive that could handle huge numbers, this is what I wrote:

var smallNums = ['zero', 'one', 'two', 'three', 'four', 'five', 'six', 'seven', 'eight', 'nine', 'ten', 'eleven', 'tweleve', 'thirteen', 'fourteen', 'fifteen', 'sixteen', 'seventeen', 'eighteen', 'nineteen'];
var suffixes = {"trillion": 1000000000000, "billion": 1000000000, "million": 1000000, "thousand": 1000, "hundred": 100};
var tens = {"ninety":90, "eighty":80, "seventy":70, "sixty":60, "fifty":50, "fourty":40, "thirty":30, "twenty":20}

function inWords (num) {
  sections = [];

  for (var word in suffixes) {
    var suffix_val = suffixes[word];
    if (num >= suffix_val) {
      suffix_multiplier = Math.floor(num / suffix_val);
      var toPush = inWords(suffix_multiplier) + " " + word;
      sections.push(toPush);
      num %= suffix_val;
    }
  }

  for (var word in tens) {
    var ten_val = tens[word];
    if (num >= ten_val) {
      sections.push(word);
      num -= ten_val;
    }
  }

  if (num > 0 || sections.length == 0) {
    sections.push(smallNums[num]);
  }
  return sections.join(' ');
}

The problem is, instead of outputting "one thousand two hundred thirty four", it's outputting, in this case, "two two hundred thirty four". I've triple checked the logic, and I'm thinking this has to do with a variable scope issue. Basically, it looks like all of the variables (like, say the sections array) are the same across levels of recursion.

So it dives into recursion when the first loop hits the line with toPush , and then updates the upper-level's variables from inside the lower level.

What makes this clear is if I throw a console.log(sections) after the toPush assignment. If the variables were just scoped to one "level" of the recursive function, the first log of sections would be empty, cause nothing in that level had filled it with anything, but it is, in fact "[one]".

At any rate the question was how to deal with this in recursive programming with Javascript. Can I specify that a variable should not be global or available to recursions within? Or, if not, what's the Javascript-y way of dealing with something like this?

This was a hell of a weird/unexpected bug to find out (I'm new to JS and didn't see this scoping issue coming), and I'd appreciate it if anyone has any suggestions.

Answer 1

sections is a global variable, thats why it's the same. Write a var in front of it.