Designing JavaScript APIs
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This document discusses best practices for designing JavaScript APIs. It covers topics like securing APIs using OAuth 2 and CORS for authorization, following HATEOAS principles to allow for automation by providing state transitions and links to next actions, and designing APIs to be stateless by sending complete representations in requests. The goal is to build APIs that are secure, easy to use and integrate, and allow developers to automate complex workflows.
!["links": [
{
"href":"https://api.sandbox.paypal.com/v1/payments/
authorization/6H149011U8307001M",
"rel":"self",
"method":"GET"
},{
"href":"https://api.sandbox.paypal.com/v1/payments/
authorization/6H149011U8307001M/capture",
"rel":"capture",
"method":"POST”
},{
"href":"https://api.sandbox.paypal.com/v1/payments/
authorization/6H149011U8307001M/void",
"rel":"void",
"method":"POST”
}
]](https://image.slidesharecdn.com/2014febconfoodesigningjavascriptapis-140228090705-phpapp02/85/Designing-JavaScript-APIs-34-320.jpg)
![The System Should be Stateless
Send complete object to only make 1 request
{ "id": "PAY-17S8410768582940NKEE66EQ",
"create_time": "2013-01-31T04:12:02Z",
"update_time": "2013-01-31T04:12:04Z",
"state": "approved",
"intent": "sale",
"payer": {...},
"transactions": [{...}],
"links": [{...}] }](https://image.slidesharecdn.com/2014febconfoodesigningjavascriptapis-140228090705-phpapp02/85/Designing-JavaScript-APIs-37-320.jpg)
Designing JavaScript APIs
- 1. Designing JavaScript APIs Jonathan LeBlanc (@jcleblanc) Global Head of Developer Evangelism at PayPal
- 2. API? SDK?
- 3. Automation?
- 4. What JavaScript Can Feel Like
- 7. Keeping Private Keys Private
- 8. Not Providing a Hacked Experience
- 9. How Did We Used to Do It?
- 11. Flash / iFrame Proxies
- 14. A Modern Approach OAuth 2 Tight Access Control CORS Easy Access Control
- 15. OAuth 2 User Agent Flow
- 16. Redirect the User to Log In Prepare the Redirect URI Authorization Endpoint client_id response_type (token) scope redirect_uri Browser Redirect Redirect URI
- 17. User Agent Flow: Redirect var auth_uri = auth_endpoint + "?response_type=token" + "&client_id=" + client_id + "&scope=profile" + "&redirect_uri=" + window.location; $("#auth_btn").attr("href", auth_uri);
- 18. Extract the Access Token Fetch the Hash Mod access_token refresh_token expires_in Extract Access Token
- 19. User Agent Flow: Hash Mod Extract the Access Token from the Hash http://site.com/callback#access_token=rBEGu1FQr5 4AzqE3Q&refresh_token=rEBt51FZr54HayqE3V4a& expires_in=3600 var hash = document.location.hash; var match = hash.match(/access_token=(w+)/);
- 20. Get Privileged API Resources Set Request Headers + URI Resource Endpoint Header: token type + access token Header: accept data type HTTPS Request
- 21. User Agent Flow: Get Resources Making an Authorized Request $.ajax({ url: resource_uri, beforeSend: function (xhr) { xhr.setRequestHeader('Authorization', 'OAuth ' + token); xhr.setRequestHeader('Accept', 'application/json'); }, success: function (response) { //use response object } });
- 22. CORS Easy Access Control
- 23. Cross Origin Issues and Options Access to other domains / subdomains is restricted (same origin policy) JSONP to request resources across domains Only supports HTTP GET requests Cross-origin resource sharing (CORS) Supports additional range of HTTP requests
- 24. Can you use it? http://caniuse.com/cors Support: 79.42% Partial support: 8.84% Total: 88.26%
- 25. How Does it Work? Site sends Origin header to server OPTIONS /v1/oauth2/token HTTP/1.1 Origin: http://jcleblanc.com Access-Control-Request-Method: PUT Host: api.sandbox.paypal.com Accept-Language: en-US Connection: keep-alive ...
- 26. How Does it Work? Server responds with matching Access-Control-Allow-Origin header Access-Control-Allow-Origin: http://jcleblanc.com Access-Control-Allow-Methods: GET, POST, PUT Content-Type: text/html; charset=utf-8
- 27. A Lil’ Bit O’ Automation
- 28. Uniform Interface Sub-Constraints Resource Identification Resources must be manipulated via representations Self descriptive messages Hypermedia as the engine of application state
- 29. Uniform Interface Sub-Constraints Resource Identification Resources must be manipulated via representations Self descriptive messages Hypermedia as the engine of application state
- 30. HATEOAS
- 31. How we Normally Consume APIs
- 32. Using HATEOAS to Automate
- 33. How HATEOAS Works You make an API request curl -v -X GET https://api.sandbox.paypal.com/v1/payments/authoriz ation/2DC87612EK520411B -H "Content-Type:application/json" -H "Authorization:Bearer ENxom5Fof1KqAffEsXtx1HTEK__KVdIsaCYF8C"
- 35. How do we Make it Work with JS? Open Path Library (what to do next) Hierarchy of Requests
- 36. Object Chaining
- 37. The System Should be Stateless Send complete object to only make 1 request { "id": "PAY-17S8410768582940NKEE66EQ", "create_time": "2013-01-31T04:12:02Z", "update_time": "2013-01-31T04:12:04Z", "state": "approved", "intent": "sale", "payer": {...}, "transactions": [{...}], "links": [{...}] }
- 38. Resources and Representations Manipulate a concept (e.g. payment) with the intended state
- 39. Chaining Actions The first request builds the action object Subsequent calls manipulate the object var paymentObj = getPreAuth(paymentID) .getNextAction() .processNext(); //build pay object //next HATEOAS link //process action
- 40. In Summation Security needs to allow you to work the browser security model Always assume statelessness Build to allow your developers to automate complexities
- 41. Thanks! Questions? http://slideshare.com/jcleblanc Jonathan LeBlanc (@jcleblanc) Global Head of Developer Evangelism at PayPal
Editor's Notes
- #8: Keeping private keys private
- #24: JSONP can cause XSS issues where the external site is compromised, CORS allows websites to manually parse responses to ensure security
- #27: Behind the server scene, the server looks up the application in their records to verify that the application matches what is on file against the application location making the request
- #31: Hypermedia as the engine of application state
- #36: How do you improve this structure to make it useable for automation?
- #37: Resources must be manipulated via representations. This goes back to the stateless principles
- #40: REST principle of using objects applied to chaining multiple objects together