如何找到丢失的 obj 并记录它们？

Question

我正在遍历一些数据，但有时我并不是每个 state 都在dictionary中，我怎样才能获得所有这些缺失状态的列表？

const result = data.map(function(item) {
  const ditem = dictionary.find(d => d.state == item.state);
  if(ditem) {
    return {
      ...item,
      "lat": ditem.lat ,
      "long": ditem.long
    }
  }
  return item;

});

$("pre").html(JSON.stringify(result, null, 2));

Answer 1

let missingStates = []; //to store missingStates

const result = data.map(function(item) {
  const ditem = dictionary.find(d => d.state == item.state);
  if(ditem) {
    return {
      ...item,
      "lat": ditem.lat ,
      "long": ditem.long
    }
  }
  missingStates.every(e=>e!=item) && missingStates.push(item) //You can push them over here
  return item;

});

console.log(missingStates) //this will log out all missingStates;

$("pre").html(JSON.stringify(result, null, 2));

Answer 2

您可以使用Array.prototype.filter列出缺失的状态：

const missingStates = data.filter(
    dataItem => !dictionary.some(dictionaryItem => dictionaryItem.state === dataItem.state)
);