function getHTTPObject() {
	var req;

	try {
		if (window.XMLHttpRequest) {
			var req = new XMLHttpRequest();

			if (req.readyState == null) {
				req.readyState = 1;
				req.addEventListener("load", function () {
					req.readyState = 4;
					if (typeof req.onReadyStateChange == "function")
						req.onReadyStateChange();
				}, false)
			}
			return req;
		}

 		if (window.ActiveXObject) {
			var prefixes = ["MSXML2", "Microsoft", "MSXML", "MSXML3"];

			for (var i = 0; i < prefixes.length; i++) {
			try {
			    req = new ActiveXObject(prefixes[i] + ".XmlHttp");
			    return req;
				} catch (ex) {}
			}
		}
	} catch (ex) {}
}

var http = getHTTPObject();

function trim(valor){
	valor = valor.replace(/^\s+/, '');
	valor = valor.replace(/\s+$/, '');
	return valor;
}

function verificaLimite(valor, alvo, tipo) {
	valor = trim(valor);
	if(valor.length >= 3){
		pesquisar_dados(valor, alvo, tipo)
	} else {
		campo_select = eval("document.forms[0]."+alvo);
		campo_select.options.length = 0;
		campo_select.options[0] = new Option("Digite pelo menos 3 caracteres.", 0);
		campo_select.options[0].style.color = 'red';
	}
}