async.series函数无法访问容器类的成员

Question

我在类的成员函数中使用了async.series，但无法访问此引用，因此无法访问async.series函数中该类的成员-对此有什么解决方法吗？

如何在类中声明async series模式并访问async series模式中的类成员？

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()

以下是输出：

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$1 (/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this，您将看到this就是函数。这与范围界定有关。https://www.w3schools.com/js/js_scope.asp会给你更多的信息。另一个有更多信息的地方：https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/this