How to create a template literal type from object to have keys=values?-CodePudding

I have an object

{
  foo: "bar",
  a: "b",
  roses: "red",
}

I would like to create a template literal which would give me the following possibilities:

"foo=bar" | "a=b" | "roses=red"

So basically, key=value

What I've done so far is:

type Foo = `${keyof typeof obj}=${typeof obj[keyof typeof obj]}`;

But this give me every possible combination:

"foo=bar" | "foo=b" | "foo=red" | "a=bar" | ...

I feel I need to use a generic but I'm not able to make it work

CodePudding user response：

You can use a self-indexing mapped type:

const obj = {
  foo: "bar",
  a: "b",
  roses: "red",
} as const;

type Foo = {
    [K in keyof typeof obj]: `${K}=${typeof obj[K]}`
}[keyof typeof obj];

This evaluates to:

type Foo = "foo=bar" | "a=b" | "roses=red"

Playground link