const arr = [
  { name:'plus1', age:20 },
  { name:'plus2', age:30 },
  { name:'plus3', age:40 },
]

let newArr = arr.map((val,index) => index + "⇒" + val.name + "⇒" + val.age)

console.log(newArr) //["0⇒plus1⇒20","1⇒plus2⇒30","2⇒plus3⇒40"]

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