typesafe-schema v0.5.0

Typesafe-schema

Typesafe-schema allows you to validate a plain old JavaScript object against a schema and obtained a well typed value in return.

It has zero dependencies and can be used either in a node.js or browser environment.

Install

Add typesafe-schema to your package.json.

With npm:

npm i -S -E typesafe-schema

With yarn:

yarn add -S -E typesafe-schema

API

• newValidator(schema: T) => { validate: (value: any, strict?: bool) => Result<TypeOf<T>>, schema }

Usage

Typesafe-schema provide more type safety if your TypeScript strict flag is set to true in your tsconfig.json. You can still use this library without this option, but some schema modifiers such as Optional and Nullable loose their benefit from a type checking point of view.

An example is always worth a thousand words:

import { EnumObj, Obj, STRING, NUMBER, Str } from 'typesafe-schema';
import { newValidator } from 'typesafe-schema';


// Our API can returns either a JSON object
// of this shape:
//
//      {
//          "result": "success",
//          "token": "fbe7cdc7-5c89-40ac-ae78-36f241e2f230"
//      }
//
// or of this shape:
//
//      {
//          "result": "success",
//          "errCode": "1023",
//          "message": "Invalid username or password"
//      }
//
const myAPI = newValidator(EnumObj(
    Obj({
        result: Str('success'),
        token: STRING,
    }),
    Obj({
        result: Str('error'),
        errCode: NUMBER,
        message: STRING,
    }),
));


function doRequest() {

    // Execute a request or get some data you want to validate
    // At this point data is "any"
    const data = ajax(...);

    // Validate the data, an optional 'strict' argument can
    // be provided to reject value that have extra properties
    const result = myAPI.validate(data);

    if (result.type === 'success') {

        // typedData is the same object as data
        // but typed! =)
        const typedData = result.value;

        // Do something with typedValue
        typedData.result  // This has type "error" | "success"
        typedData.errCode // This is a compile error! :)
                          // We need to make sure that typedValue.result
                          // is equal to 'error' first
    } else {

        // Display or do something with the reason explaining why the
        // validation failed.
        console.log(result.reason);
    }
}

Schema can also be reused:

import { Enum, Arr, Obj, STRING, NUMBER, Str } from 'typesafe-schema';
import { newValidator } from 'typesafe-schema';

export const user = newValidator(Obj({
    id: NUMBER,
    name: STRING,
    role: Enum('admin', 'regular', 'bot'),
    apiKey: Optional(STRING),
}));

// Each element in the list must satisfy the user schema.
export const userList = newValidator(Arr(user.schema));

// They can be reused anywhere...
export const device = newValidator(Obj({
    id: NUMBER,
    hostname: STRING,
    owner: user.schema,
}));

Reference