Return Unique Set of Fields in Object Array in ES6

Question

I have an array:

animals = [
 {name:"Dog", color_id:1, color:"Red" ....},
 {name:"Cat", color_id:2, color: "Blue"....}, 
 {name:"Fish", color_id:3, color:"Purple"...}, 
 {name:Mouse, color_id:2, color:"Blue" ...}
]

I need to return a list with unique colors:

colorList = [{value:1, label:"Red"}, {value:2, color:"Blue"}, {value:3, color:"Purple"}]

I do this but it doesn't return the unique ids

animals.forEach(function(currAnimal){
      var i = propertyTypeOptions.findIndex(animals => animals.value == colorList.value);
      if(i <= -1){

        propertyTypeOptions.push({value: currAnimal.color_id, label:  currAnimal.color});
      }
    })

CertainPerformance · Accepted Answer · 2019-08-14 03:32:07Z

2

Because it looks like each color maps one-to-one onto a color_id, keep a set of the colors seen so far in a Set, and only add items if they haven't been seen yet:

const animals = [
 {name:"Dog", color_id:1, color:"Red" },
 {name:"Cat", color_id:2, color: "Blue"}, 
 {name:"Fish", color_id:3, color:"Purple"}, 
 {name:'Mouse', color_id:2, color:"Blue" }
];
const seenColors = new Set();

const output = animals.reduce((a, { color_id, color }) => {
  if (!seenColors.has(color)) {
    a.push({ color_id, color });
    seenColors.add(color);
  }
  return a;
}, []);

console.log(output);

answered Aug 14, 2019 at 3:32

CertainPerformance

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1 Comment

Mohammad Usman Over a year ago

I liked the approach you used here. It will also preserve the order of objects as in original array.

Eddie · Accepted Answer · 2019-08-14 03:38:24Z

1

One option is using reduce to summarize the array into an object. Use Object.values to convert the object into an array.

let animals = [{"name":"Dog","color_id":1,"color":"Red"},{"name":"Cat","color_id":2,"color":"Blue"},{"name":"Fish","color_id":3,"color":"Purple"},{"name":"Mouse","color_id":2,"color":"Blue"}]

let colorList = Object.values(animals.reduce((c, {color,color_id}) => {
  if (!c[color]) c[color] = {label: color,value: color_id};
  return c;
}, {}));

console.log(colorList);

answered Aug 14, 2019 at 3:38

Eddie

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