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JSON

JSON. 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…. JSON. JavaScript Object Notation It is intended to be minimal

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JSON

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Presentation Transcript

  1. JSON

  2. 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…

  3. 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

  4. What’s in JSON Source: http:www/json.org

  5. String • Strings • Any double quoted Unicode character • Double quote escaped using \ • Empty string represented by "" Source: http:www/json.org

  6. Number • Numbers • Integer, real, scientific • Use null for invalid/infinity Source: http:www/json.org

  7. 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

  8. 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

  9. Using JSON to Populate a Page

  10. 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

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

  12. Convert to JSON • toJSONString() converts an object to JSON

  13. 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

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