jasmine-ajax源码解析

总体概述

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() {}

辅助函数

arrayContains

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。

extend

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。

初始化语句

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。

RequestTracker

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;
    };
  }

StubTracker

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,method)) {
          return stub;
        }
      }
    };
  }

RequestStub

请求拦截在url,method同时匹配的情况下才会启动拦截。

function RequestStub(url,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,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);
    };
  }

ParamParser

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();
  }

FackXMLHttpRequest

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,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('\r\n');
      },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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