在TypeScript中，如何指定对象中值的类型？

Question

For example, suppose I have:

export function trade(positions: object) {
  ...
}

but instead of just specifying that 'positions' is an object, I want to specify that it is an object with values that must be Strings.

What is the syntax for that?

Edit:

To tighten the example, suppose I just want keys and values to all be Strings. Is there a syntax for that?

Answer 1

If you want to share the object is as wide as "has string keys, and string values" you can use an index type:

export function trade(positions: {[key: string]: string;}) {
    // ...
}

If you want to make it more specific, it may be time to create an interface - even if everything is optional - as it will give you more design-time help when creating a positions object.

interface Positions {
    x?: string;
    y?: string;
    z?: string;
    t?: string;
}

This doesn't force any of the items to be present, but you'll get good auto-completion. If the members are required, you can make them non-optional.