async.series 函数无法访问容器 class 的成员

Question

我在 class 的成员函数中使用了 async.series 但无法访问此引用，因此无法从 async.series 函数中访问 class 的成员- 有什么解决方法吗？

如何在 class 中声明 async series 模式并访问 async series 模式中的 class 成员？

async = require("async");
class X {
  constructor() {
    this.member = 1;     /*< --- member declaration*/
  }
  f(){
    async.series([      /*< --- async declaration*/
      function (cb) {
        console.log('s1')
        cb();
      },
      function (cb) {
        console.log('s2')
        console.log(this.member)      /*< --- member access failing here*/
        cb();
      }
    ], function(){
      console.log('here')
    });
  }
}

(new X()).f()

输出如下：

s1
s2
TypeError: Cannot read property 'member' of undefined
    at /home/runner/KnowledgeableFrequentStatistic/index.js:14:26
    at /home/runner/KnowledgeableFrequentStatistic/node_modules/async/dist/async.js:2948:28
    at replenish (/home/runner/KnowledgeableFrequentStatistic/node_modules/async/dist/async.js:440:21)
    at /home/runner/KnowledgeableFrequentStatistic/node_modules/async/dist/async.js:445:13
    at eachOfLimit (/home/runner/KnowledgeableFrequentStatistic/node_modules/async/dist/async.js:471:34)
    at awaitable (/home/runner/KnowledgeableFrequentStatistic/node_modules/async/dist/async.js:208:32)
    at eachOfSeries (/home/runner/KnowledgeableFrequentStatistic/node_modules/async/dist/async.js:658:16)
    at awaitable (/home/runner/KnowledgeableFrequentStatistic/node_modules/async/dist/async.js:208:32)
    at /home/runner/KnowledgeableFrequentStatistic/node_modules/async/dist/async.js:2947:9
    at awaitable (/home/runner/KnowledgeableFrequentStatistic/node_modules/async/dist/async.js:208:32)

Answer 1

这是因为您使用 function(cb) 而不是 (cb)=>{}。如果您尝试控制台日志记录 this，您将看到 this 是函数。这与范围界定有关。 https://www.w3schools.com/js/js_scope.asp will give you some more info. Another place with some more information: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/this

async.series 函数无法访问容器 class 的成员

async.series function unable to access member of container class

node.js

async.js