Javascript - How to assign the first element of an object in array to be the key of another array

Try that one

     const a = [
        { id: 1, name: "peter", city: "New City" },
        { id: 2, name: "alex", city: "New City" },
        { id: 3, name: "michael", city: "New City" }
      ];

      const b = a.map(item => {
        const { id, ...others } = item;

        return { id: { ...others } };
      });

      console.log(b);

This is a modified version of Petia's solution. @Petia: I hope you don't mind me copying your sample data.

const a = [
        { id: 11, name: "peter", city: "New City" },
        { id: 12, name: "Alex", city: "Another City" },
        { id: 31, name: "Michael", city: "Third City" }
      ], b = {};
a.forEach(obj=>{b[obj.id]=obj});

console.log(b);

In this solution the resulting object of objects will still have the id property as part of the listed objects. If required, these id properties can easily be removed by means of the following expression:

Object.values(b).forEach(obj=>{delete obj.id});

It is possible to use map() function and spread ... operator:

const result = a.map(s => ({[s.id]:{...s}}));

And the example:

const a = [
        { id: 10, name: "Science", Type: "Type 1" },
        { id: 20, name: "Management", Type: "Type 2" },
        { id: 30, name: "Sport", Type: "Type 3" }
      ];

const result = a.map(s => ({[s.id]:{...s}}));
console.log(result);

It's not exactly clear what you are asking but assuming that your objects contain variables and not strings this might help.

id1=1;
name1='bob'
type1='ajax'

id2=2;
name2='sid'
type2='comet'

org = [ {id1, name1,type1}, {id2, name2, type2}]


neworg={}
for(i=0;i<org.length;i++){

   id = Object.values(org[i])[0]  
   
   arr=new Array();
   
   for (j=1;j<Object.keys(org[i]).length;j++){
     arr.push(Object.values(org[i])[j])   
   }

    neworg[id]={arr}


}

console.log(neworg)