angular - TypeError : val. set is not a function (JS Map())

Question

我在执行 val.set(key, value) 时遇到了这个问题并抛出类型错误 TypeError: val.set is not a function在文件中 vendor-es2015.js .

代码(简化):

import { Storage } from '@ionic/storage';


map = new Map();

this.storage.set('sth', map);

this.storage.get('sth').then((val) => {
    val.set(key, value); //TypeError, returns { } insead of a map.
});

有趣的是，这在浏览器中运行良好，但是当它使用 Capacitor 编译到 Android 时，会抛出此错误。

配置文件

"target": "es2015",
"lib": [
  "es2018",
  "dom"
]

Answer 1

如 the documentation说:

Storage works on Strings only. However, storing JSON blobs is easy: just JSON.stringify the object before calling set, then JSON.parse the value returned from get. See the example below for more details.

可能看起来像这样(更新为 help from Bergi ):

const mapStr = JSON.stringify(Array.from(map.entries()));
this.storage.set('sth', mapStr);

this.storage.get('sth').then((val) => {
    const theMap = new Map(JSON.parse(val));
    theMap.set(key, value);
});