title: Map empty after set values in forEach. Debugger shows the array iterated over isn't empty
body: <p>If i have this code</p>
  
  <p>ArbFileProvider.js</p>
  
  <pre><code>const fs = require("fs");
  
  class ArbFile {
    constructor(arbFile) {
      this.arbFile = arbFile;
    }
    async read() {
      const arbFileContents = await fs.promises.readFile(this.arbFile);
      this._arbFileObject = JSON.parse(arbFileContents.toString());
      console.log(this._arbFileObject);
      this._getRessources();
      console.log(JSON.stringify(this.ressources));
      console.log(JSON.stringify(this.properites));
    }
  
    _getRessources() {
      const ressourcesKeys = Object.keys(this._arbFileObject).filter(
        key =&gt; key.match(/^@{1,2}/g) == undefined
      );
      console.log("ressourcesKeys", ressourcesKeys);
      this.ressources = new Map();
      ressourcesKeys.forEach(key =&gt; {
        this.ressources.set(key, {
          value: this._arbFileObject[key],
          ...(this._arbFileObject[
            Object.keys(this._arbFileObject).find(val =&gt; val == `@${key}`)
          ] || {})
        });
      });
      console.log("ressources", JSON.stringify(this.ressources));
  
      const propertiesKeys = Object.keys(this._arbFileObject).filter(
        key =&gt; key.match(/^@@/g) != undefined
      );
      this.properites = new Map();
      propertiesKeys.forEach(key =&gt; {
        this.properites.set(key.replace(/^@@/g, ""), this._arbFileObject[key]);
      });
    }
  }
  
  module.exports = ArbFile;
  </code></pre>
  
  <p>at that point</p>
  
  <pre><code>console.log(JSON.stringify(this.ressources));
  </code></pre>
  
  <p>this.ressources is an empty map. I don't know why. In the debugger I can clearly see, that is has 55 entries. I have already tried to log for example the Object.keys() of it, but it is an empty Array too.</p>
  
  <p>The arbFile parameter at the constructor is an path to an json-like ARB file.</p>
  
  <p>To call that class, I create an new instance of ArbFile and then call read() on it.</p>