你所拥有的不是一个有效的数组。如果你的目标是通过do符号来访问数据，例如digiList.egg.name，那么使用数组并不是实现这一目标的方法。你需要使用对象。假设你在每个数据元素egg、baby和intraining中有一个对象，那么你将采取以下方法：

const 
    egg = { id:"blue", name:"somename otherwise 'undefined'", eggtype:"blue", digivolution:"Punimon", image:"../Images/Blue Egg - mobile.png" },
    baby = { id:"botamon", name:"Botamon", stage:"Baby", type:"Data", preDigivolution:["green"], digivolution:["Koromon"], image: "https://www.grindosaur.com/img/games/digimon-world/digimon/12-botamon.jpg" },
    intraining = { id:"koromon", name:"Koromon", stage:"In-training", type:"Data", preDigivolution:["Botamon"], digivolution:["Agumon","Gabumon","Kunemon"], image: "https://www.grindosaur.com/img/games/digimon-world/digimon/50-koromon.jpg" },
    
    digiList = { egg, baby, intraining };
    
    console.log( digiList.egg.name, digiList.baby.name, digiList.intraining.name );

不能在数组中声明变量。
但是你可以在外部声明它，然后在内部引用它。

let egg = 1
const digiList =  [
  egg = 2, egg=4, egg=egg*3
]

console.log(digiList)

// output: [2, 4, 12]

在你的情况下，你可以参考Lalit Tyagi给出的答案，它应该能满足你的需要。

const egg = { id:"blue", name:"somename otherwise 'undefined'", eggtype:"blue", digivolution:"Punimon", image:"../Images/Blue Egg - mobile.png" };
const baby = { id:"botamon", name:"Botamon", stage:"Baby", type:"Data", preDigivolution:["green"], digivolution:["Koromon"], image: "https://www.grindosaur.com/img/games/digimon-world/digimon/12-botamon.jpg" };
const intraining = { id:"koromon", name:"Koromon", stage:"In-training", type:"Data", preDigivolution:["Botamon"], digivolution:["Agumon","Gabumon","Kunemon"], image: "https://www.grindosaur.com/img/games/digimon-world/digimon/50-koromon.jpg" };
    
const digiList = { egg, baby, intraining };
    
console.log( digiList.egg.name );

const egg = { id:"blue", name:"somename otherwise 'undefined'", eggtype:"blue", digivolution:"Punimon", image:"../Images/Blue Egg - mobile.png" };
const baby = { id:"botamon", name:"Botamon", stage:"Baby", type:"Data", preDigivolution:["green"], digivolution:["Koromon"], image: "https://www.grindosaur.com/img/games/digimon-world/digimon/12-botamon.jpg" };
const intraining = { id:"koromon", name:"Koromon", stage:"In-training", type:"Data", preDigivolution:["Botamon"], digivolution:["Agumon","Gabumon","Kunemon"], image: "https://www.grindosaur.com/img/games/digimon-world/digimon/50-koromon.jpg" };
    
const digiList = { egg, baby, intraining };
    
console.log( digiList.egg.name );

const digiList = [
 [           
   {
     id:"blue",
     eggtype:"blue",
     digivolution:"Punimon",
     image:"../Images/Blue Egg - mobile.png"
    },        
],    

[
 {
   id:"botamon",
   name:"Botamon",
   stage:"Baby",
   type:"Data",
   preDigivolution:["green"],
   digivolution:["Koromon"],
   image: "https://www.grindosaur.com/img/games/digimon-world/digimon/12-botamon.jpg"
  },

 [
 {
  id:"koromon",
  name:"Koromon",
  stage:"In-training",
  type:"Data",
  preDigivolution:["Botamon"],
  digivolution:["Agumon","Gabumon","Kunemon"],
  image: "https://www.grindosaur.com/img/games/digimon-world/digimon/50-koromon.jpg"
 }
]
]
]

const[egg, baby] = digiList;

const[,intraining] = baby;