longshotlabs/js-message-box

A package for defining and getting validation error messages, with support for Meteor Tracker reactivity

MessageBox

An NPM package for defining and getting validation error messages in JavaScript. Meteor apps can pass in Tracker to get reactive language selection.

Installation

$ npm i --save message-box

Usage

Defining Messages

You can define global defaults if necessary:

MessageBox.defaults({
  initialLanguage: 'en', // optional; default is 'en'
  messages: {
    en: {
      errorType: '{{name}} is invalid' || function,
      errorType: {
        _default: '{{name}} is invalid' || function,
        fieldName: '{{name}} is invalid' || function,
      }
    },
  }
});

Otherwise create your MessageBox instance like this:

const messageBox = new MessageBox({
  initialLanguage: 'en', // optional; default is 'en'
  messages: {
    en: {
      errorType: '{{name}} is invalid' || function,
      errorType: {
        _default: '{{name}} is invalid' || function,
        fieldName: '{{name}} is invalid' || function,
      }
    },
  }
});

And update the messages object as necessary (for example if different packages are adding their own messages for different languages):

messageBox.messages({
  en: {
    errorType: '{{name}} is invalid' || function,
    errorType: {
      _default: '{{name}} is invalid' || function,
      fieldName: '{{name}} is invalid' || function,
    }
  },
});

messages does a deep extend on the existing messages.

For any of the ways you can set messages, the message can be either a string or a function that returns a string. If it's a string, it may contain handlebars placeholders for anything in the error object or anything passed in the context option of the message function. If it's a function, it will receive a single context argument that has all the same properties that are available as handlebars variables.

Example

MessageBox.defaults({
  initialLanguage: 'en',
  messages: {
    en: {
      required: '{{label}} is required',
      minString: '{{label}} must be at least {{min}} characters',
      maxString: '{{label}} cannot exceed {{max}} characters',
      minNumber: '{{label}} must be at least {{min}}',
      maxNumber: '{{label}} cannot exceed {{max}}',
      minNumberExclusive: '{{label}} must be greater than {{min}}',
      maxNumberExclusive: '{{label}} must be less than {{max}}',
      minDate: '{{label}} must be on or after {{min}}',
      maxDate: '{{label}} cannot be after {{max}}',
      badDate: '{{label}} is not a valid date',
      minCount: 'You must specify at least {{minCount}} values',
      maxCount: 'You cannot specify more than {{maxCount}} values',
      noDecimal: '{{label}} must be an integer',
      notAllowed: '{{value}} is not an allowed value',
      expectedType: '{{label}} must be of type {{dataType}}',
      regEx: function ({
        label,
        type,
        regExp,
      }) {
        // See if there's one where exp matches this expression
        let msgObj;
        if (regExp) {
          msgObj = _.find(regExpMessages, (o) => o.exp && o.exp.toString() === regExp);
        }

        const regExpMessage = msgObj ? msgObj.msg : 'failed regular expression validation';

        return `${label} ${regExpMessage}`;
      },
      keyNotInSchema: '{{name}} is not allowed by the schema',
    },
  }
});

Getting a Message

To get a message, you pass a single ValidationError error to the message function.

Here is a Meteor-specific example:

Template.foo.events({
  'submit': (event, instance) => {
    Meteor.call('method', (err) => {
      if (ValidationError.is(err)) {
        err.details.forEach((fieldError) => {
          instance.state.set(`error-${fieldError.name}`: messageBox.message(fieldError));
        });
      }
    });
  }
});

See [https://github.com/meteor/validation-error] for details about the ValidationError type.

By default, this function returns the message for the current language as set with initialLanguage or setLanguage. However, you can instead specify a particular language:

const message = messageBox.message(error, {
  language: 'pl',
});

Context

In the "Defining Messages" example, the placeholders like label and min must be in the error object or provided in the context option when calling messages:

const message = messageBox.message(error, {
  context: {
    label: getSomeLabelFor(error.name),
  },
});

Changing the Message Language

messageBox.setLanguage('en');

Reactivity in Meteor

If you use this in a Meteor app, you can make the messages reactive. Pass Tracker into the constructor:

const messageBox = new MessageBox({
  messages: { ... },
  tracker: Tracker,
});

Then when you change the language, any call to messageBox.message() that does not specify a language and is in a reactive context will rerun.

Template

By default (and historically) the substitution of strings is made using {{}}, you can change this by passing the interpolate and escape options:

const messageBox = new MessageBox({
  messages: { ... },
  interpolate: /{{{([^\{\}#][\s\S]+?)}}}/g, // default
  escape: /{{([^\{\}#][\s\S]+?)}}/g; // default
});

It is also possible (but I would not recommend) to use logic within messages by using the evaluate option:

var SUGGESTED_EVALUATE = require('MessageBox').SUGGESTED_EVALUATE
// or
import { SUGGESTED_EVALUATE } from 'MessageBox';

const messageBox = new MessageBox({
  messages: {
    en: {
      conditional: '{{# if (value) { }}true{{# } else { }}false{{# } }}',
    }
  },
  evaluate: SUGGESTED_EVALUATE,
});