Partially flattening a JavaScript object

Question

I have a JavaScript object that I receive from an API that I cannot modify. I would like to use this data within a tool, but the tool only accepts values stored on the root level of the object eg I cannot use dot notation to access the value of a key a level down.

Based on the example below, I'd like to be able to access shape.colour , but by referencing something like shape__colour instead, from a new JSON object.

Example starting object:

[{
  "id" : 12345,
  "size" : 40,
  "shape": {
     "colour" : 'yellow',
     "dimension" : '2D'
  }
},
{
  "id" : 12346,
  "size" : 50,
  "shape": {
     "colour" : 'blue',
     "dimension" : '3D'
  }
}]

What I need it to look like:

[{
  "id" : 12345,
  "size" : 40,
  "shape__colour": 'yellow',
  "shape__dimension" : '2D;'
  }
},
{
  "id" : 12346,
  "size" : 50,
  "shape__colour": 'blue',
  "shape__dimension" : '3D'
  }
}]

Other examples of object flattening functions that I've come across seem to produce a single level array (removing the objects altogether), whereas I need to keep the individual objects, but for the data inside them to be on one level.

Any help would be greatly appreciated!

Answer 1

Another map function:

const result = arr.map( 
  ({shape, ...rest}) => ({ shape__colour: shape.colour, shape__dimension: shape.dimension, ...rest })
);

Or if shape has dynamic properties:

const result = arr.map(
 ({shape, ...rest}) => Object.assign(rest, ...Object.keys(shape).map(key => {["shape__"+key] : shape[key]}))
);

Answer 2

You can use map to return a new array with the flattened shape properties:

let result = arr.map(({id, size, shape}) => {
  return {
    id,
    size,
    shape_colour: shape.colour,
    shape_dimension: shape.dimension
  }
});

Note: you can also destructure the shape object in the arguments list:

let result = arr.map(({
  id,
  size,
  shape: { colour: shape_colour, dimension: shape_dimension }
}) => {
  return {
    id,
    size,
    shape_colour,
    shape_dimension,
  }
});