javascript - 仅当第一个对象没有这些键时，才将一个 JavaScript 对象中的键添加到另一个对象中

Question

function extend(obj1, obj2) {

  var obj2Keys = Object.keys(obj2);
  var obj2Values = Object.values(obj2);

  var obj1Keys = Object.keys(obj1);
  var obj1Values = Object.keys(obj1);
  
  var newObj = {};

  for(var i=0; i<obj1Keys.length; i++) {
    if(obj1Keys[i] !== obj2Keys[i]) {
      

    }
  }
  
}

var obj1 = {
  a: 1,
  b: 2
};
var obj2 = {
  b: 4,
  c: 3
};

extend(obj1, obj2);

console.log(obj1); // --> {a: 1, b: 2, c: 3}
console.log(obj2); // --> {b: 4, c: 3}

/*

 1. Add any keys that are not in the 1st object.
 2. If the 1st object already has a given key, ignore it  (do not
    overwrite the property value).
 3. Do not modify the 2nd object at all.

*/

嘿伙计们，正在努力解决这个问题。我确信我正在以最低效的方式这样做。我正在努力比较这些对象的索引..有什么帮助吗？我最初使用 for in 循环，但我无法从概念上理解我在做什么，哈哈。有点卡在这一点上。

Answer 1

const firstObject = {a:1,b:2,c:3}
const secondObject = {a:11,b:22,c:33,d:44}
var newObject = {...secondObject,...firstObject}

console.log(newObject)

结果:

{"a":1,"b":2,"c":3,"d":44}