HttpRequest.js

//https://developer.mozilla.org/pt-BR/docs/Web/API/XMLHTTPRequest
//https://developer.mozilla.org/pt-BR/docs/Web/API/XMLHttpRequest/Usando_XMLHttpRequest
//https://www.w3schools.com/js/js_ajax_http.asp
class AjaxRequest {
	constructor() {
		if(window.XMLHttpRequest)
		{
			try
			{
				this.request = new XMLHttpRequest();
			}
			catch(e)
			{
				throw new Error(e);
			}
		}
		else
		{
			if(window.ActiveXObject)
			{
				try
				{
					this.request = new ActiveXObject("Xsxml2.XMLHTTP");
				}
				catch(e1)
				{
					try
					{
						this.request = new ActiveXObject("Microsoft.XMLHTTP");
					}
					catch(e2)
					{
						throw new Error(e1+"\n"+e2);
					}
				}
			}
			else
			{
				if(window.createRequest)
				{
					try
					{
						this.request = window.createRequest();
					}
					catch(e)
					{
						throw new Error(e);
					}
				}
			}
		}

	/*
	 * If we didn't succeed in making the request object, alert
	 * the caller of the problem.
	 */
		if(!this.request)
		{
			throw new Error("Couldn't create an XMLHttpRequest\n");
		}
	}
	abort(){
		this.request.abort();
	}
	getAllResponseHeaders(){
		this.request.getAllResponseHeaders();
	}
	overrideMimeType(mime){
		this.request.overrideMimeType(mime);
	}
	setRequestHeader(header, value){
		this.request.setRequestHeader(header, value);
	}
}

function JSONasyncRequest(url) {
	var that = this;
	var is_finished = false;
	var status = 0;
	var HttpReq = new AjaxRequest();
	this.result = {};
	this.url = (url)?url:"";
	this.onfinished = function(req,parent){};
	this.isfinished = function(){
		return is_finished;
	};
	this.status = function(){
		return status;
	};
	HttpReq.request.onreadystatechange = function() {
		if(this.readyState!==this.DONE)	{
			return;
		}
		else {
			is_finished = true;
		}
		status = this.status
		if(this.status==200) {
			try
			{
				that.result = JSON.parse(this.responseText);
				that.onfinished(this,that);
			}
			catch(e)
			{
				throw new Error(e);
				return;
			}
		}
	};
	this.get = function(){
		HttpReq.request.open("GET", this.url, true);
		HttpReq.request.send();
	}
}