替换数组中的索引

I'm trying to understand how array works in typescript and I'm struggling to find any solutions on how to replace the index inside an array by a variable, for example with the datas as show below I would like to replace all index numbers by the part_id variable that is inside each index :

例如，对于第一个索引，我想使用part_id等的26作为替代，而不是[0]。

这是一个代码示例（数据来自API，我获取了API返回的数组的副本并对其进行了修改，以便可以对它们执行forEach，而PatchValue则将onInit设置为值）

Component.ts

 initQuot(){
    this.service.checkExistQuot().subscribe(res => {
      this.quotArray = res;
      this.quotDetails = res.quotation.quotationdetail;
      let group = {};

      this.copy.forEach((val, index)=>
      {
        group[`longueur_${index}`] = '';
        group[`quantity_${index}`] = '';
        group['diameter1'] = '';
        group['diameter2'] = '';

      });
      this.dropForm = this.formBuilder.group(
        group
      );
 this.quotDetails.forEach( (myArray, index) => {
        this.copy.forEach( array1Ttem => {

          this.quotDetails.forEach( array2Item => {

            if(array1Ttem.part_id == array2Item.part_id){
              for (var i = 0; i < this.copy.length; i++) {
                this.copy[myArray.part_id] = this.copy[index];
                console.log(this.copy);
                let patchValue = {};
                this.copy[i].longueur = myArray.longueur; 
                this.copy[i].quantity = myArray.quantity; 
                patchValue[`longueur_${index}`] = this.copy[index].longueur;
                patchValue[`quantity_${index}`] = this.copy[index].quantity;
                this.dropForm.patchValue(patchValue);
              }
            }
            else{
                   console.log("No values matched");
            }

          })
        });
 })
    })
  }

如果有人知道解决方案/我应该怎样看待我的问题，我将不胜感激，谢谢