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VASTParser

The VASTParser class provides a parser to manage the parsing (parseVAST method) of VAST documents.

VASTClient has to be intended as the preferred way to manage a sequence of VAST requests on a higher level, while VASTParser offers a set of method to follow in more detail the parsing process.

Use an instance of this class directly only if you don't need any control on multiple calls, otherwise access it through an instance of VASTClient.

Error tracking

Whenever an error occurs during the VAST parsing, the parser will call automatically all related tracking error URLs. Reported errors are:

  • no_ad: The VAST document is empty
  • VAST error 101: VAST schema validation error.
  • VAST error 301: Timeout of VAST URI provided in Wrapper element.
  • VAST error 302: Wrapper limit reached.
  • VAST error 303: No VAST response after one or more Wrappers.

Constructor

The constructor signature is:

constructor()

Example

To get an instance of VASTParser, simply import it and create one using the constructor:

import { VASTParser } from 'vast-client'

// With default values
const vastParser = new VASTParser();

Events

VASTParser extends a custom EventEmitter, therefore is possible to add event listeners. Here is the list of event emitted by the class:

VAST-error

Event is triggered whenever there is an unsupported, empty VAST or a parsing error. It carries the following data:

  • ERRORCODE: Number
  • ERRORMESSAGE: String [optional]
  • extensions: Array [optional]
  • system: Object [optional]
vastParser.on('VAST-error', ({ ERRORCODE, ERRORMESSAGE, extensions, system }) => {
  // Deal with the error
});

VAST-warning

Event is triggered when the VAST required values are missing according to IAB specifications. It carries the following data:

  • message: String
  • parentElement: String
  • specVersion: Number
vastParser.on('VAST-warning', ({ message, parentElement, specVersion }) => {
  // Deal with the warning
});

VAST-resolving

Event is triggered when fetchVAST function is called, before the fetching started. It carries the following data:

  • url: String
  • previousUrl: String|Null
  • wrapperDepth: Number
  • maxWrapperDepth: Number
  • timeout: Number
  • wrapperAd: Ad
vastParser.on('VAST-resolving', ({ url, wrapperDepth, previousUrl }) => {
  // Access to the info
});

VAST-resolved

Event is triggered when fetchVAST function is called, after the fetching was done. It carries the following data:

  • url: String
  • previousUrl: String|Null
  • wrapperDepth: Number
  • error: Error|Null
  • duration: Number
  • byteLength: Number|undefined
  • statusCode: Number|undefined
vastParser.on('VAST-resolved', ({ url, error }) => {
  // Access to the info
});

VAST-ad-parsed

Event is triggered when parseVastXml function is called, when an Ad tag has been parsed. It carries the following data:

  • url: String
  • wrapperDepth: Number
  • type: 'ERROR'|'WRAPPER'|'INLINE'
  • adIndex: Number|undefined
vastParser.on('VAST-ad-parsed', ({ url, wrapperDepth, type,adIndex }) => {
  // Access to the info
});

Public Methods 💚

trackVastError(urlTemplates, errorCode, ...data)

Tracks the error provided in the errorCode parameter and emits a VAST-error event for the given error.

Parameters

  • urlTemplates: Array - An Array of url templates to use to make the tracking call
  • errorCode: Object - An Object containing the error data
  • data: Object - One (or more) Object containing additional data

fetchVAST(url, wrapperDepth = 0, previousUrl = null, wrapperAd = null)

Fetches a VAST document for the given url. Returns a Promise which resolves with the fetched xml or rejects with an error, according to the result of the request.

Parameters

  • url: String - The url to request the VAST document
  • wrapperDepth: Number - Number of wrappers that have occurred
  • previousUrl: String - The url of the previous VAST
  • wrapperAd: Ad - Previously parsed ad node (Wrapper) related to this fetching.

Events emitted

  • VAST-resolved
  • VAST-resolving

parseVAST(vastXml, options)

Parses the given xml Object into a VASTResponse. Returns a Promise which either resolves with the fully parsed VASTResponse or rejects with an Error.

This method will not proceed to any fetching, the final response will only contain the first VAST encountered. If you need to parse and follow a wrappers chain, you should use the parseVAST method from the VASTClient.

Parameters

  • vastXml: Object - An object representing an xml document
  • options: Object - An optional Object of parameters to be used in the parsing process
    • allowMultipleAds: Boolean - A boolean value that identifies whether multiple ads are allowed in the requested VAST response. This will override any value of allowMultipleAds attribute set in the VAST
    • byteLength: Number- The size of the request in bytes. Provide it with requestDuration to have a more accurate estimated bitrate.
    • resolveAll: Boolean - Allows you to parse all the ads contained in the VAST or to parse them ad by ad or adPod by adPod (default true)

Events emitted

  • VAST-resolved
  • VAST-resolving
  • VAST-warning

Example

const vastXml = (new window.DOMParser()).parseFromString(xmlStr, "text/xml");

vastParser.parseVAST(vastXml)
  .then(res => {
    // Do something with the parsed VAST response
  })
  .catch(err => {
    // Deal with the error
  });

// Or with some options
const options = {
  timeout: 5000,
  withCredentials: true,
  wrapperLimit: 7
}
vastParser.parseVAST(vastXml, options)
  .then(res => {
    // Do something with the parsed VAST response
  })
  .catch(err => {
    // Deal with the error
  });

getEstimatedBitrate()

Returns the average of the estimated bitrates in kilo bit per secondes.

Example

const options = {
  requestDuration: 200,
  byteLength: 1000,
}
vastParser.parseVAST(vastXml, options)
  .then(res => {
    vastParser.getEstimatedBitrate()
    // returns 40
  })
  .catch(err => {
    // Deal with the error
  });

Parser Utils

parseDuration(duration)

Parses a duration in the format HH:MM:SS, HH:MM:SS.mmm or SS and returns a duration in seconds.

const a = parseDuration('00:01:30.000');
console.log(a); // output: 90

const b = parseDuration('30');
console.log(b); // output: 30

const c = parseDuration(30);
console.log(c); // output: 30

const d = parseDuration('thirty');
console.log(d); // output -1

Parameter

  • duration: String - The duration represented as a string.

Private Methods ⚠️

These methods documentation is provided in order to make the parser internal logic clearer. It should not be considered as part of the class public API

parse(vastXml, options)

Parses the given xml Object into an array of unwrapped ads. Returns a Promise which resolves with the array or rejects with an error according to the result of the parsing.

Parameters

  • vastXml: Object - An object representing an xml document.
  • options: Object - An optional Object of parameters to be used in the parsing process.

parseVastXml(vastXml, options)

Parses the given xml Object into an array of ads. Returns the array or throws an Error if an invalid VAST XML is provided.

Parameters

  • vastXml: Object - An object representing an xml document.
  • options: Object - An optional Object of parameters to be used in the parsing process.

Events emitted

  • VAST-ad-parsed

resolveAds(ads = [], options)

Resolves each ad in a VAST (by calling resolveWrappers). If no ads are returned and there are remaining ads from a previous VAST (like an ad buffet), it will resolve the remaining ads.

Parameters

  • ads: Array<Ad> - An array of ads to be unwrapped in parallel.
  • options: Object - An Object of parameters to be used in the unwrapping process.

resolveWrappers(ad, wrapperDepth, previousUrl)

Resolves the wrappers for the given ad in a recursive way. Returns a Promise which resolves with the unwrapped ad or rejects with an error.

Parameters

  • ad: Ad - An ad to be unwrapped.
  • wrapperDepth: Number - The reached depth in the wrapper resolving chain.
  • previousUrl: String - The url of the previous VAST

completeWrapperResolving(vastResponse)

Takes care of handling errors when the wrappers are resolved.

Parameters

  • vastResponse: VASTResponse - A resolved VASTResponse

mergeWrapperAdData(unwrappedAd, wrapper)

Merges the data between an unwrapped ad and his wrapper.

Parameters

  • unwrappedAd: Ad - The 'unwrapped' Ad.
  • wrapper: Ad - The wrapper Ad.