Usage¶

Installing the npm module¶

  npm install --save @sozialhelden/a11yjson

Basics¶

A11yJSON's reference provides a documentation of all available interfaces and has example A11yJSON objects.

For each interface X you find in the reference, the a11yjson npm module provides

a TypeScript interface X (if you use TypeScript)
a SimpleSchema instance named XSchema to validate and sanitize objects to be correct A11yJSON

TypeScript usage¶

import { PlaceInfo } from '@sozialhelden/a11yjson';

const placeInfo: PlaceInfo = {
  geometry: {
    type: 'Point',
    coordinates: [0, 0]
  },
  properties: {
    name: 'An inaccessible place in the middle of an ocean',
    accessibility: {
      accessibleWith: {
        wheelchair: false
      }
    }
  },
}

The TypeScript compiler will validate definitions at compile time.

Validating A11yJSON objects at runtime¶

The following code imports one interface schema, PlaceInfoSchema, from A11yJSON, and validates an object against it.

If the object isn't valid, you get a detailed error object as validation result.

import { PlaceInfoSchema } from '@sozialhelden/a11yjson';

// This could be your GeoJSON feature.
const myGeoJSONFeature = {
  geometry: { … }
  properties: { … }
};

// See https://github.com/aldeed/simple-schema-js for the full documentation of how validation works.
const validationContext = PlaceInfoSchema.newContext();

// Sanitizes the input object.
// Converts types automatically if possible, e.g. convert string values to numbers where the schema demands numbers.
const sanitizedGeoJSONFeature = PlaceInfoSchema.clean(myGeoJSONFeature);

// Validate the GeoJSON feature against A11yJSON’s `PlaceInfo` schema.
validationContext.validate(sanitizedGeoJSONFeature);

if (!validationContext.isValid()) {
  const errors = validationContext.validationErrors();
  // `errors` is a JSON object with detailled validation infos about each field in the input object.
  console.log(errors);
}