通过对象数组进行映射，甚至通过与其他对象相比没有一两个键的对象进行映射

Question

Title. I can have two or three types of objects, but i would like to make reliable function to cover all other cases if any new keys/properties will be added to future objects.

Whenever i'm mapping through objects with the same properties ( obj1 , obj4 ) everything is K. The problem is when i want to make a function to map through all objects in arr with keys that may or may not be in particular object.

I was thinking about if ('key' in obj) but that wouldn't make function reliable for future, if new keys might be added unless I could analyze all object keys in arr , by creating new array with unique key objects. But if object will have 10 keys and there will be 1000+ objects in an array I assume there will be performance issues; correct me if i'm wrong.

Same goes for .hasOwnProperty() .

const arr = [
  obj1 = {
    key1: val1,
    key2: val2,
    key3: val3
  },
  obj2 = {
    key3: val3
  },
  obj3 = {
    key1: val4,
    key2: val5,
    key3: val1
  },
  obj4 = {
    key1: val6,
    key2: val7
  }
]

Answer 1

Instead of gussing the keys that an object could have, you can use Object.keys or a for...in loop to dynamically get or loop through keys of an object. Like this:

 var obj = { "key1": 2, "key2": 3, "key-unknown": 5 } console.log("METHOD 1:"); var keys = Object.keys(obj); console.log("obj has these keys: ", keys); console.log("\\nMETHOD 2:"); for(var key in obj) { console.log("'" + key + "' is a key"); } 

Using the above two methods you can safely and dynamically use only the keys that the object has and not use a set of predefined static keys that may or may not be in the object and that could be fewer than what the object actually has.

Answer 2

From a wild guess you may be in need of a function such as;

 function fillMissingKeys(a){ var keys = a.reduce((k,o) => Object.assign(k,Object.keys(o)),[]) .reduce((o,k) => (o[k] = null,o),{}); return a.map(o => Object.assign({},keys,o)); } var arr = [ obj1 = { key1: "val1", key2: "val2", key3: "val3" }, obj2 = { key3: "val3" }, obj3 = { key1: "val4", key2: "val5", key3: "val1", key4: "val8" }, obj4 = { key1: "val6", key2: "val7" } ]; console.log(fillMissingKeys(arr))