javascript - 在 ES6 中返回对象数组中唯一的字段集

Question

我有一个数组:

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" ...}
]

我需要返回一个具有唯一颜色的列表:

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

我这样做，但它不会返回唯一的 ID

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});
      }
    })

Answer 1

因为看起来每种颜色都一对一地映射到 color_id，所以将迄今为止看到的一组颜色保留在 Set 中，并且仅添加尚未看到的项目:

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);