andor
Small (<1kb) library for utilizing type safe and predictable methods to deal with conditional statements.
Contents
Installation
- Using npm -
npm install @antivixen/andor - Using yarn -
yarn add @antivixen/andor - Using pnpm -
pnpm add @antivixen/andor
Methods
-
getEvaluation<T>:
const result = getEvaluation({
case: true,
and: () => "True",
or: () => "False",
});
console.log(result);
// result === "True"Generic type is optional, however you might need to specify in case the return type is a union type, otherwise you'll gent an error:
const result = getEvaluation<string | null>({
case: false,
and: () => "True",
or: {
case: true,
and: () => "False",
or: () => null,
},
});
console.log(result);
// result === "False"and / or method in the scheme might be either a function or another scheme object:
type Scheme = {
case: boolean // any other types passing through will be converted to boolean
and() {
// either function or Scheme
}
or(){
//either function or Scheme
}
}-
getCase<T, I>: Functional alternative to JSSwitch Statement
type Case = "True" | "False";
const value: Case = getValueFromSomewhere();
const result = getCase({
switch: value,
default: "It's unknown",
cases: { True: "It's true", False: "It's false" },
});Generics are optional, if you'd like to be more specific go ahead with `getCase<Options, Result>':
const result = getCase<"True" | "False", "It's true" | "It's false">({
switch: value,
default: "It's unknown",
cases: { True: "It's true", False: "It's false" },
});See some advanced use cases in Examples
Examples
Here are some particular cases for using the methods
-
getEvaluation:
type Status = "Guest" | "User" | "Editor" | "Admin";
let isUserAuthorised;
let isAdmin;
let isEditor;If you need to get the user status, based on the provided variables you have the following options:
const userStatus: Status = isUserAuthorised
? isAdmin
? "Admin"
: isEditor
? "Editor"
: "User"
: "Guest";Not a great idea given it's not just super hard to follow the flow, but also should be forbidden in eslint
let userStatus: Status;
if (isUserAuthorised) {
if (isAdmin) {
userStatus = "Admin";
} else if (isEditor) {
userStatus = "Editor";
} else {
userStatus = "User";
}
} else {
userStatus = "Guest";
}This case clearly needs a separate method, which is + 1 level of abstraction, additionally not a great choice flow / immutability wise
const userStatus = ((): Status => {
if (isUserAuthorised) {
if (isAdmin) {
return "Admin";
}
if (isEditor) {
return "Editor";
}
return "User";
}
return "Guest";
})();You might recall the good old IIFE and come up with a much better construction. However, it can be a bit inconvenient to read in certain edge cases
const userStatus = getEvaluation<Status>({
case: isUserAuthorised,
or: () => "Guest",
and: {
case: isAdmin,
and: () => "Admin",
or: {
case: isEditor,
and: () => "Editor",
or: () => "User",
},
},
});The getEvaluation method provides a clear scheme of all possible cases, and the returning functions can have side effects, such as acting as a middleware if necessary.
-
getCase: Yet to be written..