jasmine-ajax源码解析

摘要：总体概述主要五个对象组成请求伪造对象请求跟踪对象请求拦截对象用作对伪造的请求做出响应。请求拦截跟踪对象参数解析辅助函数函数结构很明显，判定一个数组是否包含某一个值。主要负责值的解析。若决定调用，则遍历结束，返回该对象。

jasmine-ajax主要五个对象组成：

请求伪造对象(FackXMLHttpRequest)：

function FakeXMLHttpRequest() {}

请求跟踪对象(RequestTracker)：

function RequestTracker() {}

请求拦截对象(RequestStub)：用作对伪造的AJAX请求做出响应。

function RequestStub(url, stubData, method) {}

请求拦截跟踪对象(StubTracker):

function StubTracker() {}

参数解析(ParamParser)：

function ParamParser() {}

function arrayContains(arr, item) {
for (var i = 0; i < arr.length; i++) {
  if (arr[i] === item) {
    return true;
  }
}
return false;
}

函数结构很明显，判定一个数组是否包含某一个值。

function extend(destination, source, propertiesToSkip) {
    propertiesToSkip = propertiesToSkip || [];
    for (var property in source) {
      if (!arrayContains(propertiesToSkip, property)) {
        destination[property] = source[property];
      }
    }
    return destination;
  }

此函数实现对象扩展，propertiesToSkip参数为source中需排除掉的键，余下的键值对覆盖写入destination。

  if (typeof window === "undefined" && typeof exports === "object") {
    exports.MockAjax = MockAjax;
    jasmine.Ajax = new MockAjax(exports);
  } else {
    window.MockAjax = MockAjax;
    jasmine.Ajax = new MockAjax(window);
  }

首先判定是否commonjs环境，不是则传递window变量。在describe内部，即可访问通过jasmine.Ajax使用MockAjax对象。

其实结构非常明显，使用jasmine.Ajax.requests即可访问到RequestTracker对象,然后通过first, mostRecent, at, filter 等方法获取仿造的request对象，多用于对HTTP请求对象进行判定，如方法，路径，数据，headers等等，需要重点关注。reset, track手动调用意义不大，前者用于重置变量环境，后者在生成伪造XHR时调用。

 function RequestTracker() {
    var requests = [];

    this.track = function(request) {
      requests.push(request);
    };

    this.first = function() {
      return requests[0];
    };

    this.count = function() {
      return requests.length;
    };

    this.reset = function() {
      requests = [];
    };

    this.mostRecent = function() {
      return requests[requests.length - 1];
    };

    this.at = function(index) {
      return requests[index];
    };

    this.filter = function(url_to_match) {
      if (requests.length === 0) { return []; }
      var matching_requests = [];

      for (var i = 0; i < requests.length; i++) {
        if (url_to_match instanceof RegExp &&
            url_to_match.test(requests[i].url)) {
            matching_requests.push(requests[i]);
        } else if (url_to_match instanceof Function &&
            url_to_match(requests[i])) {
            matching_requests.push(requests[i]);
        } else {
          if (requests[i].url === url_to_match) {
            matching_requests.push(requests[i]);
          }
        }
      }
      return matching_requests;
    };
  }

通过jasmine.Ajax.stubs即可访问到StubTracker对象，主动调用意义不大。reset方法用于变量环境重置，addStub方法在生成RequestStub对象时调用。findStub在xhr.open()调用时，判定是否定义过response。

  function StubTracker() {
    var stubs = [];

    this.addStub = function(stub) {
      stubs.push(stub);
    };

    this.reset = function() {
      stubs = [];
    };

    this.findStub = function(url, data, method) {
      for (var i = stubs.length - 1; i >= 0; i--) {
        var stub = stubs[i];
        if (stub.matches(url, data, method)) {
          return stub;
        }
      }
    };
  }

请求拦截在url, stubData, method同时匹配的情况下才会启动拦截。

 function RequestStub(url, stubData, method) {
    var normalizeQuery = function(query) {
      return query ? query.split("&").sort().join("&") : undefined;
    };

    if (url instanceof RegExp) {
      this.url = url;
      this.query = undefined;
    } else {
      var split = url.split("?");
      this.url = split[0];
      this.query = split.length > 1 ? normalizeQuery(split[1]) : undefined;
    }

    this.data = normalizeQuery(stubData);
    this.method = method;

    this.andReturn = function(options) {
      this.status = options.status || 200;

      this.contentType = options.contentType;
      this.responseText = options.responseText;
    };

    this.matches = function(fullUrl, data, method) {
      var matches = false;
      fullUrl = fullUrl.toString();
      if (this.url instanceof RegExp) {
        matches = this.url.test(fullUrl);
      } else {
        var urlSplit = fullUrl.split("?"),
            url = urlSplit[0],
            query = urlSplit[1];
        matches = this.url === url && this.query === normalizeQuery(query);
      }
      return matches && (!this.data || this.data === normalizeQuery(data)) && (!this.method || this.method === method);
    };
  }

主要负责值的解析。paramParsers参数为parser对象数组。findParser遍历paramParsers，通过test属性判定是否启用对应的parse方法处理数据。若决定调用，则遍历结束，返回该对象。add方法一般会通过jasmine.Ajax.addCustomParamParser(parser)调用，优先级上，后添加的>先添加的>默认的。

  function ParamParser() {
    var defaults = [
      {
        test: function(xhr) {
          return (/^application/json/).test(xhr.contentType());
        },
        parse: function jsonParser(paramString) {
          return JSON.parse(paramString);
        }
      },
      {
        test: function(xhr) {
          return true;
        },
        parse: function naiveParser(paramString) {
          var data = {};
          var params = paramString.split("&");

          for (var i = 0; i < params.length; ++i) {
            var kv = params[i].replace(/+/g, " ").split("=");
            var key = decodeURIComponent(kv[0]);
            data[key] = data[key] || [];
            data[key].push(decodeURIComponent(kv[1]));
          }
          return data;
        }
      }
    ];
    var paramParsers = [];

    this.add = function(parser) {
      paramParsers.unshift(parser);
    };

    this.findParser = function(xhr) {
        for(var i in paramParsers) {
          var parser = paramParsers[i];
          if (parser.test(xhr)) {
            return parser;
          }
        }
    };

    this.reset = function() {
      paramParsers = [];
      for(var i in defaults) {
        paramParsers.push(defaults[i]);
      }
    };

    this.reset();
  }

代码过长，分段说明。

FakeXMLHttpRequest
实例化后，即添加进入requestTracker，便于后期访问。

function FakeXMLHttpRequest() {
  requestTracker.track(this);
  this.requestHeaders = {};
  this.overriddenMimeType = null;
}

原型继承
此处感觉比较好玩，是继承真的XMLHttpRequest对象，只是去掉几个特殊键值对，后面会进行处理。

var iePropertiesThatCannotBeCopied = ["responseBody", "responseText", "responseXML", "status", "statusText", "responseTimeout"];
    extend(FakeXMLHttpRequest.prototype, new window.XMLHttpRequest(), iePropertiesThatCannotBeCopied);

Request伪造
熟悉原生ajax的应该很容易看懂。重点在于，send方法调用时，会立即在stubs里寻找匹配当前url,method,data的响应拦截器，如果预定义过了，则会立刻传递给response函数进行响应，否则需要之后手动调用response函数进行响应。

    extend(FakeXMLHttpRequest.prototype, {

      open: function() {
        this.method = arguments[0];
        this.url = arguments[1];
        this.username = arguments[3];
        this.password = arguments[4];
        this.readyState = 1;
        this.onreadystatechange();
      },

      setRequestHeader: function(header, value) {
        if(this.requestHeaders.hasOwnProperty(header)) {
          this.requestHeaders[header] = [this.requestHeaders[header], value].join(", ");
        } else {
          this.requestHeaders[header] = value;
        }
      },

      overrideMimeType: function(mime) {
        this.overriddenMimeType = mime;
      },

      abort: function() {
        this.readyState = 0;
        this.status = 0;
        this.statusText = "abort";
        this.onreadystatechange();
      },

      readyState: 0,

      onload: function() {
      },

      onreadystatechange: function(isTimeout) {
      },

      status: null,

      send: function(data) {
        this.params = data;
        this.readyState = 2;
        this.onreadystatechange();

        var stub = stubTracker.findStub(this.url, data, this.method);
        if (stub) {
          this.response(stub);
        }
      },

      contentType: function() {
        return findHeader("content-type", this.requestHeaders);
      },

      data: function() {
        if (!this.params) {
          return {};
        }

        return paramParser.findParser(this).parse(this.params);
      },

      getResponseHeader: function(name) {
        return findHeader(name, this.responseHeaders);
      },

      getAllResponseHeaders: function() {
        var responseHeaders = [];
        for (var i in this.responseHeaders) {
          if (this.responseHeaders.hasOwnProperty(i)) {
            responseHeaders.push(i + ": " + this.responseHeaders[i]);
          }
        }
        return responseHeaders.join("
");
      },

      responseText: null,

      response: function(response) {
        if (this.readyState === 4) {
          throw new Error("FakeXMLHttpRequest already completed");
        }
        this.status = response.status;
        this.statusText = response.statusText || "";
        this.responseText = response.responseText || "";
        this.readyState = 4;
        this.responseHeaders = response.responseHeaders ||
          {"Content-Type": response.contentType || "application/json" };

        this.onload();
        this.onreadystatechange();
      },

      responseTimeout: function() {
        if (this.readyState === 4) {
          throw new Error("FakeXMLHttpRequest already completed");
        }
        this.readyState = 4;
        jasmine.clock().tick(30000);
        this.onreadystatechange("timeout");
      }
    });

    return FakeXMLHttpRequest;
  }

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