Does Ajax need XML? The X in Ajax once stood for XML Now x is - - PDF document

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Does Ajax need XML? The X in Ajax once stood for XML Now x is - - PDF document

Feb 26, 2023 373 likes •460 views

JSON Venkat Subramaniam svenkat@cs.uh.edu 1 Does Ajax need XML? The X in Ajax once stood for XML Now x is more like ? Whatever thats appropriate XML has its advantages and disadvantages Very expressive, but too noisy,

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Venkat Subramaniam – svenkat@cs.uh.edu

JSON

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Venkat Subramaniam – svenkat@cs.uh.edu

Does Ajax need XML?

  • The X in Ajax once stood for XML
  • Now x is more like ? Whatever that’s

appropriate

  • XML has its advantages and

disadvantages

– Very expressive, but too noisy, large, slow…

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Venkat Subramaniam – svenkat@cs.uh.edu

JSON

  • JavaScript Object Notation
  • It is intended to be minimal
  • It is a textual notation of data
  • JavaScript is a superset of JSON
  • YAML is a superset of JSON

– YAML decoder and JavaScript interpreter can be used as JSON decoder

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Venkat Subramaniam – svenkat@cs.uh.edu

What’s in JSON

Source: http:www/json.org

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Venkat Subramaniam – svenkat@cs.uh.edu

String

  • Strings

– Any double quoted Unicode character – Double quote escaped using \ – Empty string represented by ""

Source: http:www/json.org

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Venkat Subramaniam – svenkat@cs.uh.edu

Number

  • Numbers

– Integer, real, scientific – Use null for invalid/ infinity

Source: http:www/json.org

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Venkat Subramaniam – svenkat@cs.uh.edu

Object

  • Objects: More of a hashmap notation

– { "keyname": JSONValue, "keyname": JSONValue,… } – JSONValue may be any of the JSON value types including other objects

Source: http:www/json.org

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Venkat Subramaniam – svenkat@cs.uh.edu

Arrays

  • Arrays

– Sequence of values – [ JSONValue, JSONValue, JSONValue, … ] – Index is decided by implementation (like Java can use 0, VB can use 1, JSON doesn’t care) – JSONValue may be any JSON value type including objects and arrays

Source: http:www/json.org

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Venkat Subramaniam – svenkat@cs.uh.edu

Using JSON to Populate a Page

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Venkat Subramaniam – svenkat@cs.uh.edu

Concerns with eval

  • eval sends the JSON text (or any text) to

the Java compiler

  • May not be safe
  • Use only if trusted source
  • What’s the alternative
  • parseJSON only parses JSON text
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Venkat Subramaniam – svenkat@cs.uh.edu

parseJSON

  • Available from

http: / / www.json.org/ json.js

  • Parses only JSON text and is fast

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Venkat Subramaniam – svenkat@cs.uh.edu

Convert to JSON

  • toJSONString() converts an object to

JSON

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Venkat Subramaniam – svenkat@cs.uh.edu

More Convenience

  • More convenient processing functions are

sprouting up

  • There is also proposal for JSONRequest
  • bject to be standardized by browsers

– http: / / json.org/ JSONRequest.html