Increment operator returns NaN

Question

I am trying to increment a variable using the ++ operator but I keep getting NaN as a result and I'm not sure why. Here is my code:

var wordCounts = { };
var x = 0
var compare = "groove is in the heart";
        var words = compare.split(/\b/);
        for(var i = 1; i < words.length; i++){
            if(words[i].length > 2){
                wordCounts["_" + words[i]]++;
            }
        }


alert(wordCounts.toSource());

Answer 1

The value of wordCounts["_" + words[i]] is initially undefined so when you ++ it, it gives you NaN. Just change your code to:

if (wordCounts["_" + words[i]]) {
    wordCounts["_" + words[i]]++;
} else {
    wordCounts["_" + words[i]] = 1;
}