Count Occurrence of each letter in a string

by Matt Dunn

JavaScript

//count total number of each letter in a string
function countLetters(str) {
    var counts = {};
    var ch, len, index, count;
    for (index = 0; index < str.length; ++index) {
        ch = str.charAt(index);
        count = counts[ch];
        counts[ch] = count ? count + 1 : 1;
    }
    console.log(counts);
}