AjaxLib

// requires common.js
// Namespace Ajax
var Ajax = {
    init: function (defaults) {
        function ajax(opts) {
            opts = extend({
                method: 'GET',
                url: '',
                params: {}, // параметры URL
                cache: ajax.defaults.cache,
                async: true,
                user: '',
                password: '',
                timeout: ajax.defaults.timeout,
                responseType: 0, // string
                overrideMimeType: 0, // string
                withCredentials: ajax.defaults.withCredentials,
                headers: {},
                data: null,
            }, opts);
            var methods = {};
            var xhr = new XMLHttpRequest;
            var params = clone(opts.params);
            if (opts.method === 'GET' && opts.cache === false) {
                params.__t = new Date().getTime(); // url?__t=1410142975437
            }
            var url = opts.url;
            if (!isEmpty(params)) {
                url = url + (url.indexOf('?') == -1 ? '?' : '&') + buildQuery(params);
            }
            xhr.open(opts.method, url, opts.async, opts.user, opts.password);
            if (opts.timeout) {
                xhr.timeout = opts.timeout;
            }
            if (opts.responseType) {
                xhr.responseType = opts.responseType;
            }
            if (opts.overrideMimeType) {
                xhr.overrideMimeType(opts.overrideMimeType);
            }
            xhr.withCredentials = opts.withCredentials;
            var headers = extend(Ajax.normalizeHeaders(ajax.defaults.headers)
                , Ajax.normalizeHeaders(opts.headers));
            for (var h in headers) {
                xhr.setRequestHeader(h, headers[h]);
            }
            xhr.onload = function () {
                if (xhr.status >= 200 && xhr.status < 300) {
                    if (methods.done) {
                        methods.done(xhr.response, xhr);
                    }
                } else {
                    if (methods.fail) {
                        methods.fail(xhr.response, xhr.status, xhr);
                    }
                }
                if (methods.always) {
                    methods.always(xhr.response, xhr.status, xhr);
                }
            };
            xhr.send(opts.data);
            var promises = {};
            each(['done', 'fail', 'always'], function (key) {
                promises[key] = function (cb) {
                    methods[key] = cb;
                    return promises;
                };
            });
            return promises;
        }
        ajax.get = function(url, opts) {
            opts = opts ? clone(opts) : {};
            opts.method = 'GET';
            opts.url = url;
            return ajax(opts);
        };
        ajax.post = function(url, data, opts) {
            opts = opts ? clone(opts) : {};
            opts.method = 'POST';
            opts.url = url;
            if (false === data instanceof FormData) {
                opts.headers = opts.headers || {};
                opts.headers['content-type'] = 'application/x-www-form-urlencoded';
                data = buildQuery(data);
            }
            opts.data = data;
            return ajax(opts);
        };
        ajax.defaults = extend({
            headers: {},
            timeout: 0,
            withCredentials: false,
            cache: true,
        }, defaults);
        return ajax;
    },
    normalizeHeaders: function (headers) {
        var r = {};
        for (var k in headers) {
            if (hasOwn(headers, k)) {
                r[trim(k).toLowerCase()] = headers[k];
            }
        }
        return r;
    },
};

var ajax = Ajax.init();
// f(args).done(function () {}).fail(function () {}).always(function () {});
// ajax(opts)
// ajax.get(url[, opts])
// ajax.post(url, data[, opts])
// GET /search?q=%D1%81%D0%B8%D1%81%D1%8C%D0%BA%D0%B8&__t=1410145166266
// ajax.get('/search', {cache: false, params: {q: 'сиськи'}}).done(function (data) { ... });