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Javascript – JSONP

JSONP is a method for sending JSON data without worrying about cross-domain issues.

JSONP does not use the XMLHttpRequest object.

JSONP uses the <script> tag instead.

JSONP Intro

JSONP stands for JSON with Padding.

Requesting a file from another domain can cause problems, due to cross-domain policy.

Requesting an external script from another domain does not have this problem.

JSONP uses this advantage, and request files using the script tag instead of the XMLHttpRequest object. Continue reading Javascript – JSONP

Javascript JSON PHP

A common use of JSON is to read data from a web server, and display the data in a web page.

This chapter will teach you how to exchange JSON data between the client and a PHP server.

The PHP File

PHP has some built-in functions to handle JSON.

Objects in PHP can be converted into JSON by using the PHP function json_encode(): Continue reading Javascript JSON PHP

Javascript JSON Server

A common use of JSON is to exchange data to/from a web server.

When receiving data from a web server, the data is always a string.

Parse the data with JSON.parse(), and the data becomes a JavaScript object.

Sending Data

If you have data stored in a JavaScript object, you can convert the object into JSON, and send it to a server:

Example

const myObj = {name: "John", age: 31, city: "New York"};
const myJSON = JSON.stringify(myObj);
window.location = "demo_json.php?x=" + myJSON;

Continue reading Javascript JSON Server

Javascript JSON Array Literals

This is a JSON string:

'["Ford", "BMW", "Fiat"]'

Inside the JSON string there is a JSON array literal:

["Ford", "BMW", "Fiat"]

Arrays in JSON are almost the same as arrays in JavaScript.

In JSON, array values must be of type string, number, object, array, boolean or null.

In JavaScript, array values can be all of the above, plus any other valid JavaScript expression, including functions, dates, and undefined.

Continue reading Javascript JSON Array Literals

Javascript JSON Object Literals

This is a JSON string:

'{"name":"John", "age":30, "car":null}'

Inside the JSON string there is a JSON object literal:

{"name":"John", "age":30, "car":null}

JSON object literals are surrounded by curly braces {}.

JSON object literals contains key/value pairs.

Keys and values are separated by a colon.

Keys must be strings, and values must be a valid JSON data type:

string
number
object
array
boolean
null

Each key/value pair is separated by a comma.

It is a common mistake to call a JSON object literal “a JSON object”.

JSON cannot be an object. JSON is a string format.

The data is only JSON when it is in a string format. When it is converted to a JavaScript variable, it becomes a JavaScript object.

Continue reading Javascript JSON Object Literals

Javascript JSON.stringify()

A common use of JSON is to exchange data to/from a web server.

When sending data to a web server, the data has to be a string.

You can convert any JavaScript datatype into a string with JSON.stringify().

Stringify a JavaScript Object

Imagine we have this object in JavaScript:

const obj = {name: "John", age: 30, city: "New York"};

Use the JavaScript function JSON.stringify() to convert it into a string.

const myJSON = JSON.stringify(obj);

The result will be a string following the JSON notation.

myJSON is now a string, and ready to be sent to a server: Continue reading Javascript JSON.stringify()

Javascript JSON.parse()

A common use of JSON is to exchange data to/from a web server.

When receiving data from a web server, the data is always a string.

Parse the data with JSON.parse(), and the data becomes a JavaScript object.

Example – Parsing JSON

Imagine we received this text from a web server:

'{"name":"John", "age":30, "city":"New York"}'

Use the JavaScript function JSON.parse() to convert text into a JavaScript object:

const obj = JSON.parse('{"name":"John", "age":30, "city":"New York"}');

Make sure the text is in JSON format, or else you will get a syntax error.

Use the JavaScript object in your page: Continue reading Javascript JSON.parse()

JSON vs XML

Both JSON and XML can be used to receive data from a web server.

The following JSON and XML examples both define an employees object, with an array of 3 employees:

JSON Example

{"employees":[
  { "firstName":"John", "lastName":"Doe" },
  { "firstName":"Anna", "lastName":"Smith" },
  { "firstName":"Peter", "lastName":"Jones" }
]}

XML Example

<employees>
  <employee>
    <firstName>John</firstName> <lastName>Doe</lastName>
  </employee>
  <employee>
    <firstName>Anna</firstName> <lastName>Smith</lastName>
  </employee>
  <employee>
    <firstName>Peter</firstName> <lastName>Jones</lastName>
  </employee>
</employees>

Continue reading JSON vs XML

Javascript JSON Syntax

The JSON syntax is a subset of the JavaScript syntax.

JSON Syntax Rules

JSON syntax is derived from JavaScript object notation syntax:

Data is in name/value pairs
Data is separated by commas
Curly braces hold objects
Square brackets hold arrays

Continue reading Javascript JSON Syntax

Javascript JSON – Introduction

JSON Example

This example is a JSON string:

'{"name":"John", "age":30, "car":null}'

It defines an object with 3 properties:

name
age
car

Each property has a value.

If you parse the JSON string with a JavaScript program, you can access the data as an object:

let personName = obj.name;
let personAge = obj.age;

Continue reading Javascript JSON – Introduction