conversant/ad-libs.js

'use strict';
/**
 * @module xhr
 * @desc Cross browser wrapper for XMLHttpRequest. If you need Cookies and HTTP Auth data to be included in the request, you must set withCredentials to true in the options.
 * @example
 * ```js
 * var xhr = require('adlibs/lib/xhr');
 * ```
 */

/* globals ActiveXObject */

/**
 * Create the XHR object that works for this specific browser.
 * @returns {*|XMLHttpRequest|ActiveXObject}
 * @private
 */
var createXHR = function () {
    var xhr;

    // IE 9+, Modern Browsers
    try {
        xhr = new window.XMLHttpRequest();
    } catch(e) {}

    // IE 7.x - 8.x
    if (!xhr) {
        try {
            xhr = new ActiveXObject('Msxml2.XMLHTTP.6.0');
        } catch(e) {}
    }

    // IE 5, IE 6
    if (!xhr) {
        try {
            xhr = new ActiveXObject('Microsoft.XMLHTTP');
        } catch(e) {}
    }

    return xhr;
};

/**
 * @param {{url: String, method: String, withCredentials: Boolean, responseType: String}} options
 * @param {Function} callback - Executed on response with the signature (status: Number, body: String).
 * @returns {{xhr: XMLHttpRequest, send: Function}}
 * @example
 * ```js
 * // performs a GET request
 * var resp = xhr({url: 'www.example.com'}).send();
 *
 * ```
 *
 */
var xhr = function (options, callback) {
    var method = options.method || 'GET',
        withCredentials = options.withCredentials || false,
        url = options.url,
        responseType = options.responseType || 'text',
        xmlHttpRequest = createXHR();

    return {
        xhr: xmlHttpRequest,

        send: function() {
            if (!xmlHttpRequest) {
                return callback(0, '');
            }

            xmlHttpRequest.open(method, url);
            xmlHttpRequest.withCredentials = withCredentials;
            xmlHttpRequest.responseType = responseType;

            xmlHttpRequest.onreadystatechange = function () {
                if (xmlHttpRequest.readyState === 4) {
                    var status = xmlHttpRequest.status,
                        body = responseType === 'text' ? xmlHttpRequest.responseText : xmlHttpRequest.response;

                    if (typeof body === 'undefined') {
                        body = '';
                        status = 500;
                    }

                    callback(status, body);
                }
            };

            xmlHttpRequest.send();

            return this;
        }
    };
};

/**
 * @desc Determines if CORS is supported.
 * @static
 * @returns {Boolean} returns whether CORS is supported
 */
var supportsCORS =  function() {
    return 'withCredentials' in createXHR();
};

module.exports = xhr;

module.exports.supportsCORS = supportsCORS;