@dotmh/dynomight

Dyn-O-Might

A small (but one day hopefully mighty) wrapper round AWS DynomoDB to do commonly required things.

WARNING this is very much a work in progress! Not all of DynomoDB is supported yet. I tend to add new features and support more of dynomoDB as I need it. Use at own risk

Installation

to install use NPM

npm i @dotmh/dynomight

Usage

Dynomight is just a standard JS class called DynoMight and can be used in essentially two ways.

Directly

You can create a new instance of the class and then use that directly

const DynoMight = require('@dotmh/dynomight');
const dynomight = new Dynomight((new AWS.DynamoDB.DocumentClient()), 'someTable', {
  id: {
    required: true,
    isKey: true
  }
});

then call methods on that instance

const result = await dynomight.put(id, document);

By Extention

You can also create your own class and extend DynoMight , this is the way I tend to use it for more complex projects.

const DynoMight = require('@dotmh/dynomight');

class MyModel extends DynoMight {
  constructor() {
    super((new AWS.DynamoDB.DocumentClient()), 'someTable', {
      id: {
        required: true,
        isKey: true
      }
    });
  }
}

This allows you to add domain specific code to the class that is interacting with your DynmoDB data.

You then of course use an instance of your class to interact with Dynomdb.

const myModel = new MyModel();
const result = await myModel.put(id, document);

Definition

In the examples above we pass an instance of the AWS SDK DynamoDB Document Client, the name we want for our table and this thing called a definition. A definition is like a schema in traditional database schema. Dynomight uses this to work out how to handle operations to and from DynamoDB as well as for validation.

A defintion is a standard object that defines which fields to use, whether they are the key field and optionally some validation rules such as type or requirement.

The object key is the field name i.e. id and the value is the metadata about that field. this can include

• isKey Whether this is the document key field. Remember the warning this whole library is not complete, one of the most obvious omitions is that it doesn't support sort keys yet as I just havent needed them
• required Whether or not the field is required its is a boolean true it is required, false it is not
• type The JS type of the field if you were to run typeof NOTE this does know the difference between an object and array.

When you only want to define a field , you can use a short hand for required and just set the value to a boolean i.e. if there is a field called to and it is required to: true would be all that is needed.

Example

{
  from: {
    required: true,
    isKey: true
  },
  to: true,
  fromCode: true,
  toCode: true
}

Any other field meta data can be stored here that you want, if you add extra functionality then you can store meta data for the field that it requires. For example I have a plugin that uses more advanced validation using validate.js a definition for that was

const defintion = {
  // ... more fields
  website: {
    validation: {
      presence: false,
      type: "string",
      url: true
    }
  },
  // ... more fields
}

Hooks

Event ... or whatever you want to call them, is away of extending DynOMight to add new functionality. All operations have a pre hook and most (execpt for validation) has an after hook. Hooks get triggered automatically as the class does its works.

To bind a hook you use the on method. The method takes some hook name, and a callback function to run when the hook is triggered.

myModel.on(myModel.beforePuthHook, (data) => console.log(data));

Hook names are always JS Symbols so you need to use the class properties for hooks.

Hooks can be used to achieve all kinds of things, I added them for this very reason as I needed this functionality. One use I needed was to automatically put a "date updated" and "date created" stamp on every record. which looks like this

// class set up code 
constructor() {
  // Constructor set up code
  timestamps();
}

timestamps() {
  // Create some constants
  const DATE_CREATED = 'date-created';
  const DATE_UPDATED = 'date-updated';
  
  // Update the definition to add our new fields.
  this.definition[DATE_CREATED] = true;
	this.definition[DATE_UPDATED] = true;

  //bind to the `beforePut` hook so every time we update a record this is triggered
	this.on(this.beforePutHook, (params) => {
    // Get the time now
    const now = new Date().toUTCString();
    
    // If we don't have a date created then we create one and set the date created
		if (!(DATE_CREATED in params)) {
			params[DATE_CREATED] = now;
		}

    // Set the date updated to now
    params[DATE_UPDATED] = now;
    
    // Return the result This is a MUST!
		return params;
	});
}

Please note that I have changed this code slightly for the sake of this example, as using it as is would cause you to store a date in a not very useful format i.e. Tue, 23 Jun 2020 14:42:15 GMT which isn't ideal

Hook List

Hook	Description	Parameters
beforePutHook	Operation Hook - Before Put	parameters Object - The raw parameters object before it sent to DynamoDB
afterPutHook	Operation Hook - After Put	response Object - The processed response object returned by DynamoDB
beforeGetHook	Operation Hook - Before Get	parameters Object - The raw parameters object before it sent to DynamoDB
afterGetHook	Operation Hook - After Get	response Object - The processed response object returned by DynamoDB
beforeDeleteHook	Operation Hook - Before Delete	parameters Object - The raw parameters object before it sent to DynamoDB
afterDeleteHook	Operation Hook - After Delete	response Object - The processed response object returned by DynamoDB
beforeScanHook	Operation Hook - Before Scan	parameters Object - The raw parameters object before it sent to DynamoDB
afterScanHook	Operation Hook - After Scan	response Object - The processed response object returned by DynamoDB
validationHook	This hook is fired when anything calls the isValid method	event See isValid method documentation - preventDefault: Boolean (false) prevent the use of the default validation - data: Object The data that is been saved - definition : Object The definition object - tableName: String The table name - result : Array The result of the validation

Documentation

API Documentation Comming Soon - Remember its not finished 😜

Licence

This package is Treeware. If you use it in production, then we ask that you buy the world a tree to thank us for our work. By contributing to the Treeware forest you’ll be creating employment for local families and restoring wildlife habitats.

Credits

Logo design by @dotmh