JSON

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JSON
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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, large, slow

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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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Whats in JSON
Source httpwww/json.org
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String

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

Source httpwww/json.org
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Number

• Numbers
• Integer, real, scientific
• Use null for invalid/infinity

Source httpwww/json.org
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Object

• Objects More of a hashmap notation
• "keyname" JSONValue, "keyname" JSONValue,
• JSONValue may be any of the JSON value types
  including other objects

Source httpwww/json.org
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Arrays

• Arrays
• Sequence of values
• JSONValue, JSONValue, JSONValue,
• Index is decided by implementation (like Java can
  use 0, VB can use 1, JSON doesnt care)
• JSONValue may be any JSON value type including
  objects and arrays

Source httpwww/json.org
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Using JSON to Populate a Page
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Concerns with eval

• eval sends the JSON text (or any text) to the
  Java compiler
• May not be safe
• Use only if trusted source
• Whats the alternative
• parseJSON only parses JSON text

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parseJSON

• Available from http//www.json.org/json.js
• Parses only JSON text and is fast

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Convert to JSON

• toJSONString() converts an object to JSON

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More Convenience

• More convenient processing functions are
  sprouting up
• There is also proposal for JSONRequest object to
  be standardized by browsers
• http//json.org/JSONRequest.html