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var keys = ['2', '4', 'R', '2', 'd', '2'];
var result = keys.reduce(function(accum, current){
  return !accum ? current : '' + accum + current;
});
console.log(result);

app.use(function (req, res, next) {
	res.header("Access-Control-Allow-Origin", req.headers.origin);
	res.header('Access-Control-Allow-Credentials', 'true');
	res.header("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept");
	next();
});

var ajaxSettings = {
			method: form.method,
			url: form.action,
			data: JSON.stringify(data),
			//					dataType: form.method === 'get' ? 'jsonp' : 'json',
			dataType: 'json',
			contentType: 'application/json',
			processData: false,
			xhrFields: {
				withCredentials: true
			}
		};
		var ajaxRequest = $.ajax(ajaxSettings);