javascript extract certain properties from all objects in array

Question

I have an array of objects with the same properties. Each object has around a hundred properties. I want to keep only a handful of them in a new array:

var dummyArray = [{ "att1": "something", "att2": "something", ..., "att100": "something"}, { "att1": "something", "att2": "something", ..., "att100": "something"}, ...];

How can I filter/map/reduce... and extract the interesting keys?

const newDummArray = dummyArray.map(function(item) { 
    delete item.att1; 
    delete item.att3; 
    delete item.att15;
    // ... (long list)
    return item; 
});

how can I keep only att20, att30, att70, att80 for each object and delete the rest?

Answer 1

store the props you want to keep in an array then for each object transfer wanted props to a new object.

var dummyArray = [{ "att1": "something", "att2": "something", "att100": "something"}, { "att1": "something", "att2": "something", "att100": "something"}];

var propsToKeep = ["att1", "att100"];

var result = dummyArray.map(item => {
  const obj = {};
  for (const prop of propsToKeep) {
    obj[prop] = item[prop];
  }
  return obj;
})

console.log(result)

Answer 2

Use object destructuring to get the properties, and generate a new object using shorthand property names:

const dummyArray = [{ "att20": "att20", "att30": "att30", "att70": "att70", "att80": "att80"}, { "att20": "att20", "att30": "att30", "att70": "att70", "att80": "att80"}];

const result = dummyArray.map(({ att20, att30, att70, att80 }) => ({
  att20, 
  att30, 
  att70, 
  att80
}));

console.log(result);

Answer 3

I have find easiest way to do this JSON.stringify()

The JSON.stringify() method converts a JavaScript object or value to a JSON string, optionally replacing values if a replacer function is specified or optionally including only the specified properties if a replacer array is specified.

    const odata = [
      { "id": "0001", "type": "donut", "name": "Cake", "ppu": 0.55 },
      { "id": "0002", "type": "ansd", "name": "EARK", "ppu": 0.67 }
    ];
    const outdata=JSON.stringify(odata,['id','type']);
    console.log(outdata);