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Value Unions

Take another look at our last example of a literal type:

function move(direction: "north") {
  // Implementation...
}

To make it a bit more useful, let's combine that idea with a union type:

function move(direction: "north" | "south" | "east" | "west") {
  // Implementation...
}

And then let's refactor it to make a new "Direction" type that we can reuse:

type Direction = "north" | "south" | "east" | "west";

function move(direction: Direction) {
  // Implementation...
}

Assignment

At Support.ai, we're building a ticket prioritization system that needs a consistent way to categorize tickets by importance.

Create and export a new type, Priority, that is a union of four string values:
- low
- medium
- high
- critical
Update the setPriority function to accept the Priority type instead of any string.
Complete the setPriority function. It should return a number based on the Priority:
- low returns 0
- medium returns 1
- high returns 2
- critical returns 3
- By default return 0

The default case is needed so that the function's inferred return type doesn't include undefined.