Letter frequency
Solutions
Solution 1 (Click to Show/Hide)
function letterFrequency(txt) {
var cs = txt.split(''),
i = cs.length,
dct = {},
c = '',
keys;
while (i--) {
c = cs[i];
dct[c] = (dct[c] || 0) + 1;
}
keys = Object.keys(dct);
keys.sort();
return keys.map(function (c) { return [c, dct[c]]; });
}