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JSON Tutorial
Brandon Schwarzer
The JSON Format
A JSON file can be formatted in a number of different ways. Unlike YAML, JSON allows flexibility
regarding indentation of data, which allows JSON files to be easily readable with indentation or compact
without indentation. Here are a couple of examples on how JSON formatting may vary:
The difference between the “Organized” and “Compact” versions of the same data are noticeable in
readability and size. Each version would be appropriate in different situations. For example, if creating a
JSON file where users may need to read the JSON data often, the “Organized” format may be the better
choice. However, if readability is less of a factor than performance, which is the case in larger JSON files,
then the “Compact” format may work better in such a situation.
JSON Tools
There are many web tools out there to help create a JSON file using outside data. Although many web
projects update JSON files automatically there may be situations where a JSON file will need to be
created from non-JSON data before including it in a project. These tools help project members get
started in creating populated JSON files.
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Convert CSV to JSON
This tool is made for users who have data
that is comma-separated that needs to be
converted into JSON. A user can simply input
their raw data or upload a text file in order to
convert their data into JSON.
This tool has many options depending on the
format of the input data. For example, a user
can indicate whether or not the first row in
their data will be designated as column
names. Also, a user can specify what their
field-separator is or simply let the program auto-detect the field separator.
This tool will generate a JSON file as output. From there, a user can insert this JSON file into a project
and use their data as JSON. The program can also output text that displays in the program if a user
prefers to use the output JSON-formatted text elsewhere.
JSON Editor
The JSON Editor tool allows users to
create or edit JSON data in a clean,
automatically formatting interface.
Users can create a file from scratch or
upload an existing file onto the web
application for editing. JSON data can
be edited to have proper indentation or
no indentation based on user
preference. When finished editing,
users can save their work as a JSON file
to be used in a project.
JSON Lint
JSON Lint is simply a JSON validator. When creating a JSON
file by hand it is important to validate the JSON because
non-valid JSON can create issues that may not be easily
detected. JSON Lint allows users to paste a JSON string or a
URL to a JSON file to check for formatting errors. Errors will
be clearly identified with a brief error message that explains
the error.
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JSON Functions
Parsing from a JSON File
Perhaps one of the most useful and most common uses of JSON is parsing from a JSON file. What this
means is reading and processing JSON data and turning that data into an object that can be used like a
normal array.
Here is an example of what parsing from a JSON file looks like:
var xmlhttp = new XMLHttpRequest(), json – Creates XMLHttpRequest object that will eventually read a
JSON file
xmlhttp.onreadystatechange - Event that fires when load state of the XMLHttpRequest object changes
if(xmlhttp.ReadyState === 4 && xmlhttp.status === 200) – If statement for the XMLHttpRequest object
that equals true if the ReadyState is 4 (request finished and response is ready) and status is 200 (“OK”)
json = JSON.parse(xmlhttp.ResponseText); - Parses the resulting data from xmlhttp with the
ResponseText method using JSON’s parse method and assigns parsed data as an object into the json
variable.
xmlhttp.open(‘GET’, ‘users.json’, true); - Fires a GET request from the XMLHttpRequest to the
‘users.json’ file in the same directory with “true” signifying the result being handled asynchronously.
Xmlhttp.send – Sends the request off to the server.
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Parsing and accessing JSON from code
JSON code does not have to be in a separate JSON file in order to work with it in a project. This example
shows how to insert simple JSON data directly into a project and how to access specific elements once
converted into an object.
var userstext – String of JSON-formatted data
document.getElementById(“parsing”).innerHTML = obj.users[1].name + “ “ + obj.users[1].location; Uses DOM tree to access the second entry in the users column and the second entry in the location
column from the parsed JSON data.
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Stringify
A JSON string can also be generated from object data using a method called “Stringify.” Here is an
example of Stringify being used on a very simple, single-entry array object:
Var userJson = JSON.stringify(user); = Stringify method is used on the user array and assigned as a string
called userJson
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A more complex example of Stringify is below, and introduces the concept of filtering. Filtering allows
only certain columns of an object to be converted into a JSON string.
The new filter variable is an array of the names of the columns to be included in the stringify method.
The stringify method, which passes user, filter, and 3 as parameters, is stringifying user by using a filter
established by filter array with an indentation of 3 to the output string.
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Resources
Tools
JSONLint
JSON Editor
CSV to JSON
Instructions
JSON for Beginners YouTube
PHP Academy Series on JSON
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Part 2: Linting
Part 3: Parsing
Part 4: Stringify
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