javascript array-object convert one key, array value single object

Question

I have an object like this:

[ 
    { "number": 12, "string": "hi"},
    { "number": 40, "string": "bye"}
] 

I want:

{"number": [12, 40], "string": ["hi", "bye"]}

Or:

{"number": "12,40", "string": "hi,bye"}

Answer 1

You can use Array.prototype.reduce():

The reduce() method executes a reducer function (that you provide) on each member of the array resulting in a single output value.

Solution With Concatenated String:

var data = [ 
    { "number": 12, "string": "hi"},
    { "number": 40, "string": "bye"}
] 
data = data.reduce((a,c)=>{
  a.number = a.number + ',' +c.number;
  a.string = a.string + ',' +c.string;
  return a;
});
console.log(data);

Solution With Array:

var data = [ 
    { "number": 12, "string": "hi"},
    { "number": 40, "string": "bye"}
]

data = data.reduce((a,c)=>{
  a.number.push(c.number);
  a.string.push(c.string);
  return a;
}, {number:[],string:[]});
console.log(data);