Make JavaScript client work in both Node.js and browser

* Replace jQuery with SuperAgent which works in both Node.js and browser
* Use UMD pattern (returnExports.js) to make the module exporting compatible
  with all major systems: AMD, Node.js (CommonJS) and browser
* Implement support of header and form parameters. Closes #1736
* Move HTTP requesting code to `ApiClient` and allow customizing options
  in it, e.g. "basePath"
* Update unit tests accordingly and add some tests for `ApiClient`

samples/client/petstore/javascript/src/ApiClient.js

@@ -0,0 +1,146 @@
+(function(root, factory) {
+  if (typeof define === 'function' && define.amd) {
+    // AMD. Register as an anonymous module.
+    define(['superagent'], factory);
+  } else if (typeof module === 'object' && module.exports) {
+    // CommonJS-like environments that support module.exports, like Node.
+    module.exports = factory(require('superagent'));
+  } else {
+    // Browser globals (root is window)
+    if (!root.SwaggerPetstore) {
+      root.SwaggerPetstore = {};
+    }
+    root.SwaggerPetstore.ApiClient = factory(root.superagent);
+  }
+}(this, function(superagent) {
+  'use strict';
+
+  var ApiClient = function ApiClient() {
+    this.basePath = 'http://petstore.swagger.io/v2'.replace(/\/+$/, '');
+  };
+
+  ApiClient.prototype.paramToString = function paramToString(param) {
+    if (param == null) {
+      // return empty string for null and undefined
+      return '';
+    } else {
+      return param.toString();
+    }
+  };
+
+  /**
+   * Build full URL by appending the given path to base path and replacing
+   * path parameter placeholders with parameter values.
+   * NOTE: query parameters are not handled here.
+   */
+  ApiClient.prototype.buildUrl = function buildUrl(path, pathParams) {
+    if (!path.match(/^\//)) {
+      path = '/' + path;
+    }
+    var url = this.basePath + path;
+    var _this = this;
+    url = url.replace(/\{([\w-]+)\}/g, function(fullMatch, key) {
+      var value;
+      if (pathParams.hasOwnProperty(key)) {
+        value = _this.paramToString(pathParams[key]);
+      } else {
+        value = fullMatch;
+      }
+      return encodeURIComponent(value);
+    });
+    return url;
+  };
+
+  /**
+   * Check if the given MIME is a JSON MIME.
+   * JSON MIME examples:
+   *   application/json
+   *   application/json; charset=UTF8
+   *   APPLICATION/JSON
+   */
+  ApiClient.prototype.isJsonMime = function isJsonMime(mime) {
+    return Boolean(mime != null && mime.match(/^application\/json(;.*)?$/i));
+  };
+
+  /**
+   * Choose a MIME from the given MIMEs with JSON preferred,
+   * i.e. return JSON if included, otherwise return the first one.
+   */
+  ApiClient.prototype.jsonPreferredMime = function jsonPreferredMime(mimes) {
+    var len = mimes.length;
+    for (var i = 0; i < len; i++) {
+      if (this.isJsonMime(mimes[i])) {
+        return mimes[i];
+      }
+    }
+    return mimes[0];
+  };
+
+  /**
+   * Normalize parameters values:
+   *   remove nils,
+   *   keep files and arrays,
+   *   format to string with `paramToString` for other cases.
+   */
+  ApiClient.prototype.normalizeParams = function normalizeParams(params) {
+    var newParams = {};
+    for (var key in params) {
+      if (params.hasOwnProperty(key) && params[key] != null) {
+        var value = params[key];
+        if (value instanceof Blob || Array.isArray(value)) {
+          newParams[key] = value;
+        } else {
+          newParams[key] = this.paramToString(value);
+        }
+      }
+    }
+    return newParams;
+  };
+
+  ApiClient.prototype.callApi = function callApi(path, httpMethod, pathParams,
+      queryParams, headerParams, formParams, bodyParam, contentTypes, accepts,
+      callback) {
+    var url = this.buildUrl(path, pathParams);
+    var request = superagent(httpMethod, url);
+
+    // set query parameters
+    request.query(this.normalizeParams(queryParams));
+
+    // set header parameters
+    request.set(this.normalizeParams(headerParams));
+
+    var contentType = this.jsonPreferredMime(contentTypes) || 'application/json';
+    request.type(contentType);
+
+    if (contentType === 'application/x-www-form-urlencoded') {
+      request.send(this.normalizeParams(formParams));
+    } else if (contentType == 'multipart/form-data') {
+      var _formParams = this.normalizeParams(formParams);
+      for (var key in _formParams) {
+        if (_formParams.hasOwnProperty(key)) {
+          if (_formParams[key] instanceof Blob) {
+            // file field
+            request.attach(key, _formParams[key]);
+          } else {
+            request.field(key, _formParams[key]);
+          }
+        }
+      }
+    } else if (bodyParam) {
+      request.send(bodyParam);
+    }
+
+    request.end(function(error, response) {
+      if (callback) {
+        var data = response && response.body;
+        callback(error, data, response);
+      }
+    });
+
+    return request;
+  };
+
+  ApiClient.default = new ApiClient();
+
+  return ApiClient;
+}));