node system command check

doesCommandExist.js

var spawn = require('child_process').spawn;
 
function doesCommandExist (command, callback) {
    var child = spawn('type', [command]);
 
	child.on('close', function (code) {
		callback(!code);
	});
}
 
doesCommandExist('compass', function (exists) {
	console.log(exists);
});