根据密钥的存在更新对象，否则形成一个新对象：JavaScript

Question

具有以下格式的对象：

let obj = {
  p2: {
    p21: [
      {
        key1: "val1",
        value1: "val2"
      },
      {
        prop: "test",
        value: "dummy"
      }
    ]
  }
}

我基本上必须查看是否有一个具有键“ prop”的对象，并用传递的值替换。如果不存在该键，则用{ "prop" : "test" , value: passed_value}创建一个对象并将其添加到p21数组中。同样，包含键“ prop”的对象也可以出现在p21数组内的任何位置]

应该是这样的

function checkAndUpdate(replacingValue) {
    if(obj's p21 has key name "prop")
    {
      //update its "value" to the passed "replacingValue"

    }
    else //if "prop" key not present
    {
       // create an object with { "prop": "test" , value: replacingValue} and add it to p21 array        
    }  
  }

尝试过以下操作：

obj.p2.p21.map((elem) => {
    if(Object.keys(elem)[0] === "prop") 
        elem.value = updateValue;
})

Answer 1

使用.findIndex查找匹配对象的索引。如果存在，则在数组前后放置.slice数组，并在中间插入更新的对象。否则，只需将对象散布到数组中即可：

let obj = {
  "p2": {
    "p21": [{
        "key1": "val1",
        "value1": "val2",
      },
      {
        "prop": "test",
        "value": "dummy"
      }
    ]
  }
}

function checkAndUpdate(value) {
  const newObj = { prop: 'test', value} 
  const arr = obj.p2.p21;
  const index = arr.findIndex(obj => obj.hasOwnProperty('prop'));
  const newArr = index !== -1
    ? [...arr.slice(0, index), newObj, ...arr.slice(index + 1)]
    : [...arr, newObj];
  const fullNewObj = {
    ...obj,
    p2: {
      ...obj.p2,
      p21: newArr
    }
  };
  return fullNewObj;
}
console.log(checkAndUpdate('foo'));

还要检查value是否未定义，如果需要，则从数组中删除匹配的对象，只需进行适当的if检查，并根据需要对数组进行切片：

let obj = {
  "p2": {
    "p21": [{
        "key1": "val1",
        "value1": "val2",
      },
      {
        "prop": "test",
        "value": "dummy"
      }
    ]
  }
}

function checkAndUpdate(value) {
  const newObj = { prop: 'test', value} 
  const arr = obj.p2.p21;
  const index = arr.findIndex(obj => obj.hasOwnProperty('prop'));
  const newArr = (() => {
    if (index === -1) {
      if (value === undefined) {
        return arr;
      }
      return [...arr, newObj];
    }
    if (value === undefined) {
      return [...arr.slice(0, index), ...arr.slice(index + 1)];
    }
    return [...arr.slice(0, index), newObj, ...arr.slice(index + 1)];
  })();
  const fullNewObj = {
    ...obj,
    p2: {
      ...obj.p2,
      p21: newArr
    }
  };
  return fullNewObj;
}
console.log(checkAndUpdate('foo'));

Answer 2

您可以使用Array.find查找hasOwnProperty prop并更新的对象

let obj = {
  "p2": {
    "p21": [{
      "key1": "val1",
      "value1": "val2",
    },
    {
      "prop": "test",
      "value": "dummy"
    }
    ]
  }
}
function rep(value) {
  if (!value.length) {
    obj.p2.p21 = [...obj.p2.p21].filter(e => e.hasOwnProperty('prop'));
    return;
  }
  let ele = obj.p2.p21.find(e => e.hasOwnProperty('prop'));
  if (ele) {
    ele.value = value
    return;
  }
  obj.p2.p21.push({
    "prop": "test",
    value
  })
}

rep('test');
console.log(JSON.stringify(obj))
rep('');
console.log(JSON.stringify(obj))