Javascript:无法分配给只读属性'_epoch'的false

Question

我有一个方法来处理来自我的谷歌JavaScript客户端(gapi)的响应:

var processResponse = function(response) {
              result._state = 'loaded';
              response._epoch = (new Date()).getTime();
              ...

有几次我得到以下错误:

TypeError: Cannot assign to read only property '_epoch' of false
    at processResponse (http://0.0.0.0:9000/scripts/services/haparaapi.js:110:31)
    at wrappedCallback (http://0.0.0.0:9000/bower_components/angular-scenario/angular-scenario.js:20892:81)
    at http://0.0.0.0:9000/bower_components/angular-scenario/angular-scenario.js:20978:26
    at Scope.$eval (http://0.0.0.0:9000/bower_components/angular-scenario/angular-scenario.js:21967:28)
    at Scope.$digest (http://0.0.0.0:9000/bower_components/angular-scenario/angular-scenario.js:21796:31)
    at Scope.$apply (http://0.0.0.0:9000/bower_components/angular-scenario/angular-scenario.js:22071:24)
    at http://0.0.0.0:9000/bower_components/angular-gapi/modules/gapi-client.js:121:32
    at https://apis.google.com/_/scs/apps-static/_/js/k=oz.gapi.en_GB.hE_reuZ6VdE.…/ed=1/am=AQ/rs=AGLTcCPj66Crj6soG8dKJE8lBSc_RPXXKA/cb=gapi.loaded_0:604:138
    at https://apis.google.com/_/scs/apps-static/_/js/k=oz.gapi.en_GB.hE_reuZ6VdE.…/ed=1/am=AQ/rs=AGLTcCPj66Crj6soG8dKJE8lBSc_RPXXKA/cb=gapi.loaded_0:579:311
    at Object.<anonymous> (https://apis.google.com/_/scs/apps-static/_/js/k=oz.gapi.en_GB.hE_reuZ6VdE.…1/ed=1/am=AQ/rs=AGLTcCPj66Crj6soG8dKJE8lBSc_RPXXKA/cb=gapi.loaded_0:163:76) 

这个错误通常不会发生,所以我没有设法记录响应的实际情况.

错误是什么意思？我不应该为响应分配值吗？

Answer 1

看起来问题是您的processResponse()回调实际上被赋予了值false.所以基本上你试图分配一个假值的_epoch属性.

请参阅:https: //developers.google.com/api-client-library/javascript/reference/referencedocs#gapiclientRequest

从手册:

请求成功或失败时执行的回调函数.jsonResp包含解析为JSON的响应.如果响应不是JSON,则此字段将为false.

当您在严格模式('use strict')中运行javascript时,它会引发TypeError您遇到的问题:

'use strict';
var processResponse = function(response) {
    response._epoch = (new Date()).getTime();
};

processResponse(false);   // Uncaught TypeError: Cannot assign to read only property '_epoch' of false 

JSFiddle:http://jsfiddle.net/0tq6mobm/

建议您在尝试将时间戳分配给之前检查响应的值response.