MongoDB drop databases by regex

function dropdbs(regex, force) {

	force = force || false;

	regex = regex || /.*/;

	var n = 0;
	var s = 0;

	db.adminCommand( { listDatabases: 1 } ).databases.sort(function(a,b) {
		return a.name>b.name;
	}).forEach(function(d){
		if (!String(d.name).match(regex)) {
			return;
		}

		print(d.name + '\t' + humanSize(d.sizeOnDisk));
		n++;
		s += d.sizeOnDisk;

		if (!force) {
			return;
		}

		db.getSiblingDB(d.name).dropDatabase();
	});

	print("");
	print(n+" databases dropped - " + humanSize(s));

	if (!force) {
		print("");
		print("This is a dry run, to make it real, force it (second parameter true)");
	}
}

function humanSize(bytes) {
    var units = ['B', 'KiB','MiB','GiB','TiB','PiB','EiB','ZiB','YiB'];
    var z = 1024;

    var u = 0;
    while (bytes > z) {
    	u++
    	bytes /= z;
    }
    return bytes.toFixed(1) + ' ' + units[u];
}

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