在javascript数组上使用find时如何检查未定义

Question

在我使用的数组中。查找以查找对象并将其属性设置为某个值。我只想在有值的情况下设置名称。即；检查以下未定义的是我的数组，我正在使用。查找以查找对象并设置其名称。我只想在找到id==checkid的对象时进行设置。

 this.myarray.find(colDef => colDef.id === checkid).name = newname;.

Answer 1

这里有两种方法。

如果你不在乎，用火忘记风格。

如果你真的想知道，更详细的检查。

const arr = [{id:1}];

const fireAndForget = (arr, id, newName) => (arr.find(i => i.id === id)||{}).name = newName;

const checkAndNotify = (arr, id, newName) => {
  const p = arr.find(i => i.id === id);
  if(!p) return false;
  p.name = newName;
  return true;
};

console.log(checkAndNotify(arr, 2, 'test'));
console.log(checkAndNotify(arr, 1, 'test'));
console.log(arr);

console.log(fireAndForget(arr, 2, 'test2'));
console.log(fireAndForget(arr, 1, 'test2'));
console.log(arr);

Answer 2

您需要运行search作为它自己的语句，并检查结果是否被定义。如果是，请指定名称，否则不要：

let myarray = [
    {id: 100},
    {id: 10},
    {id: 5}
]

let found = myarray.find(colDef => colDef.id === 10)

if (found !== undefined){
    found.name = "some name"
} 
console.log(found)

// no id 11 found will be undefined
found = myarray.find(colDef => colDef.id === 11)
console.log(found)

Answer 3

您可以在一条语句中使用Object来实现这一点。分配如下：

let myArray = [{id: 1, name: 'Boris'}, {id: 2}]

// id 3 does not exist no changes would be made to myArray
Object.assign(myArray.find(x => x.id == 3) || {}, {name: 'Foo'})

// id 1 is there so name would be changed to 'john'
Object.assign(myArray.find(x => x.id == 1) || {}, {name: 'john'})

console.log(myArray)