In Section 18.4 it was mentioned what types are allowed as values in JSON. Organized a bit differently from above, they are:
The former three are normally, in most programming languages, referred to as primitive types. The latter two are complex, or composite types in that they group several values of various type. String, in the middle, is in some languages a primitive, in others an object.
Remember again: JSON may have grown out of JavaScript, but it is not JavaScript. It is being used by all moderne programming languages.
{
"int_min": -2147483648,
"int_max": 2147483647,
"uint_max": 4294967295,
"long_min": -9223372036854775808,
"long_max": 9223372036854775807,
"ipv6_max": 3.402823669209385e+38,
"ipv6_max_int": 340282366920938463463374607431768211455,
"num253_min": -9007199254740991,
"num253_max": 9007199254740991,
"aarhus_latitude": 56.1629,
"aarhus_longitude": 10.2039,
"nuneaton_lat": 52.5205,
"nuneaton_lon": -1.4654,
"earth_mass": 5.9723e+24,
"earth_radius": 6378000
}
The Valid numbers are seen above. Integers, positive and
negative, decimal numbers, or numbers in so called
scientific notation ie a decimal number multiplied by
a power, e for exponent, of ten.
5.9723e+24 is equivalent to
5.9723 * 1024.
{
"awake": true,
"asleep": false,
"answers": [true, true, true, false, false, true, false]
}
The possible values of booleans are, unsurprisingly,
true, and false. They might even
be arranged in an array if that could be useful.
{
"nullIsNotaValue": null
}
I prefer the interpretation that strictly speaking,
formally,
null is not a value, it is a keyword for
unknown. It does, however, appear
in JSON as a possible value in a name/value pair ;)
Please notice that true, false,
and null must be all lower case. A convention
from JavaScript.
{
"firstName": "Niels",
"middleInitial": "M",
"lastName": "Larsen",
"hobby": "Playing the Devil's advocate"
"award": "Won \"King of the Hair Splitters\" in 2015"
}Please remember that string values as well as names must be quoted with double quotes, eg ("a…b").
{
"name": {
"firstName": "Niels",
"middleInitial": "M",
"lastName": "Larsen"
},
"adresse": {
"street": "Hovedgaden",
"house": 999,
"zip": 8270,
"town": "Højbjerg"
}
}or even embedded objects
{
"person": {
"name": {
"firstName": "Niels",
"middleInitial": "M",
"lastName": "Larsen"
},
"adresse": {
"street": "Hovedgaden",
"house": 999,
"zip": 8270,
"town": "Højbjerg"
},
"occupation": "Teacher"
}
}
You will, of course, notice the similarity to literal object notation in JavaScript. This is not coincidental. Objects, however, in JSON do not allow functions. That, and the fact that names must be quoted, are probably the two biggest differences to literal objects.
{
"class": [
"Reuben",
"Simeon",
"Judah",
"Issachar",
"Zebulun",
"Benjamin",
"Dan",
"Naphtali",
"Gad",
"Asher",
"Ephraim",
"Manasseh"
]
}
An array named class containing the names of
twelve students as values. It is feasible that a student
leaves the class, and that perhaps a new student enters the
class at the same time. This would possibly result in:
{
"class": [
"Reuben",
"Simeon",
"Judah",
null,
"Zebulun",
"Benjamin",
"Dan",
"Naphtali",
"Gad",
"Asher",
"Ephraim",
"Manasseh",
{
"name": "The Lost Tribe",
"refound": 2017
}
]
}
Legal JSON? Yes, absolutely: Best practice? Absolutely not. For quite obvious reasons. How to prevent it? Use JSON schema, and validate your JSON with that.
{
"Image": {
"Width": 800,
"Height": 600,
"Title": "View from 15th Floor",
"Thumbnail": {
"Url": "http://www.example.com/image/481989943",
"Height": 125,
"Width": 100
},
"Animated" : false,
"IDs": [116, 943, 234, 38793]
}
}
[
{
"precision": "zip",
"Latitude": 37.7668,
"Longitude": -122.3959,
"Address": "",
"City": "SAN FRANCISCO",
"State": "CA",
"Zip": "94107",
"Country": "US"
},
{
"precision": "zip",
"Latitude": 37.371991,
"Longitude": -122.026020,
"Address": "",
"City": "SUNNYVALE",
"State": "CA",
"Zip": "94085",
"Country": "US"
}
]