JSON
By Marcus Lopes
Summary
•
•
•
•
•
What is JSON?
JSON vs XML
Using JSON
JSON + AJAX
JSON + JQuery
What is JSON?
•
•
•
•
Javascript Object Notation
RFC 4627
Lightweight alternative to XML
Built-in to Javascript
JSON Structure
• Object
Pair of curly brackets containing zero or more name/value
pairs.E.g.:
{ "customer":
{
"name":"Marcus",
"favoriteFood":"Burgers",
"age": 21
}
}
To find out the name for this customer, you would write:
customer.name
JSON Structure
• Arrays
Represented as square brackets and values are separated by
comas. May contain 0 or more values.E.g.:
{"customer":
{
"name":"Marcus",
"favoriteFood":[
"Burgers","Fries","Bacon"],
"age": 21
}
}
customer.favoriteFood[2] would return Bacon
JSON Structure
• Numbers
Similar to most programming languages
E.g.:
{"customer":
{
"name":"Marcus",
"numbers":[
23, 2, 1.35],
"age": 21
}
}
To find the age, you can type customer.age
JSON Structure
• Strings
Work similar to the C family of programming languages
A string begins and ends with quotation marks. E.g.:
{"customer":
{
"name":"Marcus",
"language":"Portuguese"
}
}
To find out the language, you can type customer.language
JSON Structure
• Objects
JSON objects can contain nested objects and
functions:
{"customer":
{
"myFunction":function (){alert("Hello world!");},
"numbers":[23, 2, 1.35],
"age": 21
}
}
To call the method myFunction, you can type
customer.myFunction();
JSON Structure
• Parsing
The default encoding for JSON is UTF-8
• According to its documentation, JSON shall be encoded in
Unicode.
• In order to read JSON from an AJAX request, we must
evaluate the JSON code using the eval() function.
• Parenthesis must surround the code to be evaluated to
avoid confusion between a code block and an object
E.g.: eval("({price:20})")
Links
Response: HTML, XML or JSON
http://www.quirksmode.org/blog/archives/2005/12/the_ajax_res
pon.html
JSON documentation
http://www.json.org/
PHP json_encode documentation
http://php.net/manual/en/function.json-encode.php