Can you explain the concept of the type object and its use? Some say it's like a blackbox. Which approach is better, A or B, when dealing with a parameter that may have unknown types of object keys?
A
const modifyData: (data: object) => void = data => {// perform actions }
modifyData({name: "Alice", age: 25})
B
type JSONObject = { [key: string]: string | number}
const modifyData: (data: JSONObject) => void = data => {// perform actions }
category is a classification you define as a reference. In the case of your C example, if you execute the following snippet:
const myItem:ItemCategory = itemFromList();
Object.entries(myItem).map(itemValue => { /* 'itemValue' can be either a 'string' or 'number' */ });
It is more advisable compared to example B, where itemValue would be of type any, which is a mystery in the world of TypeScript.
When you specify a category, you are defining a range of possible values that can be assigned. Depending on the usage of modify(), you can implement different category strategies.
If you are certain that the object will strictly adhere to {label:string, quantity:number} then you should define your category accordingly:
type Item = { label:string; quantity:number };
If you only know that object properties may contain either a string or a number, then you can define a category similar to your example, but utilizing a Dictionary:
type ItemCategory = Dictionary<string, string | number>;
Lastly, if you are unsure about the type held within an object, I suggest a slight adjustment by using uncertain
type ItemCategory = Dictionary<string, uncertain>;
Assigning to object will tag any property value as any, providing no safeguarding of types. Utilizing uncertain offers a slightly better level of type protection, a topic that can be explored further. Resources discussing the advantages of selecting uncertain over any are readily available.
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