Why is a JS class property overwritten?

Question

JavaScript

why can the this.process property be overwritten in the GraphMaker constructor

for (let trunk in trunks) {
                if (trunks.hasOwnProperty(trunk)) {
                  let template = [];
                  process.name = trunk;
                  template.push({name: 'in', metric: trunks[trunk].input}, {name: 'out', metric: trunks[trunk].out});
                  let Graph = new GraphMaker($this.host);
                  Graph.updateDB(process, template);
                  Graph.render(process, '12h');
                }
              }

function GraphMaker(host) {
  this.host = host;
  const $this = this;
this.updateDB = function(process, metric) {
    this.process = process;
    this.metric = metric;
    let pathToDb = dbPath(process);
 console.log(this.process);
    fs.access(pathToDb, (err) => {
      console.log(this.process);
      if (err) {}
})

1 console.log
{ group: 'asterisk', name: 'E1-i3' }
{ group: 'asterisk', name: 'TEL-IP01' }
2 console.log
{ group: 'asterisk', name: 'TEL- IP01' }
{ group: 'asterisk', name: 'TEL-IP01'
} for each for pass, a separate instance is created by the constructor, but anyway, the variable inside is somehow overwritten and after performing the asynchronous action, the last value from the for iteration is already left, why?