map() 中的打字稿错误：元素隐式具有“任何”类型，因为“字符串”类型的表达式不能用于索引类型

Question

i have an array (iotDatas) of:

interface iotData {
 id: string;
 device_id: string;
 color: number;
 ph: number
 created_at: string;
} 

a state to select between the 'color' and 'ph' properties, with a default value 'color':

const [selecetedPropriety, setSelectedPropriety] = useState('color');

and this map return a typescrip error:

const yesterdayData = iotDatas.map(iotDada => {
 return { x: iotDada.created_at, y: iotDada[selecetedPropriety]};
});

Element implicitly has an 'any' type because expression of type 'string' can't be used to index type 'ioTData'.
No index signature with a parameter of type 'string' was found on type 'ioTData'

i dont know what to do.

Thans for your help!

Answer 1

So the first thing here is that iotData is not an array, it is an object, which you are trying to access using a key of this object. I believe you can use as keyof here. Such as below, which specifies that the string is a key of iotData

iotData[selecetedPropriety as keyof iotData]