Infrastruct

Make JavaScript objects with stricter, struct-like data access.

Install

Install the dependency

# using npm
npm i --save infrastruct

# using yarn
yarn add infrastruct

Import into module

// if using ES6
import defineStruct from 'infrastruct';

// if not using ES6
const defineStruct = require('infrastruct');

What does this do and why?

The freedom to call any key on JavaScript objects can lead to lot of bugs. For example, you might have a user object that has the following structure:

const exampleUser = {
  username: 'opensourcer324',
  email: '[email protected]',
  zodiac: 'libra',
};

exampleUser.phoneNumber
//=> undefined

If you tried to access value with a key that is not username, email, or zodiac, such as phoneNumber JavaScript will simply return undefined. This is okay and reasonable in some cases, but if this user-object structure should be consistent for all users, it'd make sense to not allow for any data access other than for username, email, and zodiac, and to actually throw a runtime error if anyone tries to access another value. This can be accomplished with a struct. For example:

import defineStruct from 'infrastructure';

const createUserStruct = defineStruct(['username', 'email', 'zodiac']);

const exampleUser = createUserStruct({
  username: 'opensourcer324',
  email: '[email protected]',
  zodiac: 'libra',
});

exampleUser.phoneNumber
//=> Error: attempted to access non-existent property `phoneNumber` on struct


exampleUser.phoneNumber = '845-382-8492';
//=> Error: attempted to set non-existent property `phoneNumber` on struct

Struct creating functions defined with defineStruct will also throw a runtime error if you attempt to create a struct with params that contains any keys that weren't originally passed to defineStruct.

import defineStruct from 'infrastructure';

const createUserStruct = defineStruct(['username', 'email', 'zodiac']);

const exampleUser = createUserStruct({
  username: 'opensourcer324',
  email: '[email protected]',
  zodiac: 'libra',
  phoneNumber: '845-382-8492',
});
//=> Error: attempted to create struct with non-existent property `phoneNumber`

Are structs still objects though?

Yes! Under the hood, structs created with any defined-struct-functions are still plain JavaScript objects, and can do all the normal JavaScript object things like destructuring, using the spread syntax, getting passed to functions like Object.keys, etc.

However, anything that tries to call internal JavaScript object values on the object will not work. For example, if you tried to check the constructor of the exampleUser struct by calling exampleUser.constructor, an error would be thrown saying:

Error: attempted to access non-existent property `phoneNumber` on struct

How does it work?

When you call define struct, what you are receiving back is a function that will take whatever object you give it and wrap it in a Proxy. The Proxy basically intecepts any call made on the object that deals with property access, checks to see if the property that is trying to be accessed is valid property previousily defined when defineStruct was called, and if it is, it simply returns the value, otherwise it will throw an error.