find -E . -type f -not -regex "^\./\.git/.*" | awk 'BEGIN {FS="."} {tally[$NF]+=1} END {for (key in tally) {printf "%d: %s\n", tally[key], key}}' | sort -n -k 1,1 | tail -r

example.js

// simple and quick port of 
//
// find -E . -type f -not -regex "^\./\.git/.*"  | awk 'BEGIN {FS="."} {tally[$NF]+=1} END {for (key in tally) {printf "%d: %s\n", tally[key], key}}' | sort -n -k 1,1 | tail -r 
//

var wrench = require('wrench'),
    fs = require('fs'),
    path = require('path'),
    _ = require('lodash');


// process either current working directory or pass in as first arg
var dir = process.argv[2] || process.cwd();

// read directory listing

var files = wrench.readdirSyncRecursive(dir);

// create tally hash
var tally = {};

// walk through each file in array
files.forEach(function(fn){
    // if it's a file and it doesn't match regexp
    if (fs.statSync(path.join(dir,fn)).isFile() && !/^\.\/\.git\/.*/.test(fn)) {
        // extract file extension or just filename if no extension
        var key = path.extname(fn).substring(1) || fn;
        // record tally
        if (key in tally) {
            tally[key]++;
        }
        else {
            tally[key] = 1;
        }
    }
});

console.log(
    // turn hash (key/value) into array of key/value then sort it inversely
    _.pairs(tally).sort(function(a,b){
        if (a[1] < b[1]) return 1;
        if (a[1] > b[1]) return -1;
        return 0;
    // then take the resulting array and map it into a one-liner in the output format
    }).map(function(o){
        return o[1]+': '+o[0];
    // then take the array and join separated by newline
    }).join('\n')
);