I'm encountering an issue with TypeScript regarding my interface MentionItem. Both the id and value properties are supposed to be strings, but TypeScript is flagging them as possibly string | undefined.
Interestingly, manually checking that id and value are not undefined resolves the TypeScript error. However, when I attempt to validate for undefined values using
Object.values(dataset).includes(undefined)I'm puzzled by this TypeScript error and looking for guidance on how to rectify it.
Here's a snippet of my code:
interface MentionItem {
id: string;
value: string;
}
getItemData = (): MentionItem => {
const dataset = (this.mentionList.childNodes[this.itemIndex] as HTMLElement).dataset;
if(Object.values(dataset).includes(undefined)) {
throw new Error("Incomplete dataset")
}
return {
id: dataset.id,
value: dataset.value,
};
};
This is the TypeScript Error message:
Type 'string | undefined' is not assignable to type 'string'. Type 'undefined' is not assignable to type 'string'.ts(2322)I find it perplexing why this triggers an error, considering it should function in the same manner. Please correct me if I am mistaken:
The check that satisfies TypeScript
if(dataset.id === undefined || dataset.value === undefined) {
throw new Error("Incomplete dataset")
}
The check that upsets TypeScript
if(Object.values(dataset).includes(undefined)) {
throw new Error("Incomplete dataset")
}