Learn JS #37

JavaScript JSON


JSON is a format for storing and transporting data.

JSON is often used when data is sent from a server to a web page.


What is JSON?

  • JSON stands for JavaScript Object Notation
  • JSON is a lightweight data interchange format
  • JSON is language independent *
  • JSON is “self-describing” and easy to understand

* The JSON syntax is derived from JavaScript object notation syntax, but the JSON format is text only. Code for reading and generating JSON data can be written in any programming language.


JSON Example

This JSON syntax defines an employees object: an array of 3 employee records (objects):

JSON Example

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

The JSON Format Evaluates to JavaScript Objects

The JSON format is syntactically identical to the code for creating JavaScript objects.

Because of this similarity, a JavaScript program can easily convert JSON data into native JavaScript objects.


JSON Syntax Rules

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

JSON Data – A Name and a Value

JSON data is written as name/value pairs, just like JavaScript object properties.

A name/value pair consists of a field name (in double quotes), followed by a colon, followed by a value:

"firstName":"John"

JSON names require double quotes. JavaScript names do not.


JSON Objects

JSON objects are written inside curly braces.

Just like in JavaScript, objects can contain multiple name/value pairs:

{"firstName":"John""lastName":"Doe"}

JSON Arrays

JSON arrays are written inside square brackets.

Just like in JavaScript, an array can contain objects:

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

In the example above, the object “employees” is an array. It contains three objects.

Each object is a record of a person (with a first name and a last name).


Converting a JSON Text to a JavaScript Object

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

For simplicity, this can be demonstrated using a string as input.

First, create a JavaScript string containing JSON syntax:

let text = '{ "employees" : [' +
'{ "firstName":"John" , "lastName":"Doe" },' +
'{ "firstName":"Anna" , "lastName":"Smith" },' +
'{ "firstName":"Peter" , "lastName":"Jones" } ]}';

Then, use the JavaScript built-in function JSON.parse() to convert the string into a JavaScript object:

const obj = JSON.parse(text);

Finally, use the new JavaScript object in your page:

Example

<p id="demo"></p>

<script>
document.getElementById("demo").innerHTML =
obj.employees[1].firstName + " " + obj.employees[1].lastName;
</script>

Categories

248 Responses

  1. Hello bro!Show more!
    частный пансионат
    https://pansionat-rnd.ru/
    “Дом престарелых” – это общепринятое название для социального учреждения, которое оказывает услуги по социальной защите и помощи престарелым людям. Если вы ищете информацию о конкретном доме престарелых в Ростове-на-Дону, можете уточнить местоположение и другую информацию.
    дом престарелых в Ростове-на-Дону

    http://images.google.com.cu/url?q=https://pansionat-rnd.ru/ http://www.google.co.ma/url?q=https://pansionat-rnd.ru/ http://cse.google.ml/url?q=https://pansionat-rnd.ru/ http://www.google.co.cr/url?q=https://pansionat-rnd.ru/ https://www.google.bt/url?q=https://pansionat-rnd.ru/

  2. Prescription Drug Information, Interactions & Side. Read here.
    ivermectin 2%
    Medicament prescribing information. Definitive journal of drugs and therapeutics.

  3. drug information and news for professionals and consumers. Actual trends of drug.
    https://mobic.store/# can i purchase cheap mobic without insurance
    Top 100 Searched Drugs. Prescription Drug Information, Interactions & Side.

  4. Get information now. Learn about the side effects, dosages, and interactions.
    https://clomiphenes.com get cheap clomid online
    Medicament prescribing information. safe and effective drugs are available.

  5. Comprehensive side effect and adverse reaction information. Medicament prescribing information.
    buying propecia tablets
    Some are medicines that help people when doctors prescribe. safe and effective drugs are available.

  6. Some are medicines that help people when doctors prescribe. earch our drug database.
    drugs for ed
    Definitive journal of drugs and therapeutics. Read information now.

  7. Everything information about medication. Learn about the side effects, dosages, and interactions.
    https://edonlinefast.com best pills for ed
    Some are medicines that help people when doctors prescribe. Everything about medicine.

  8. Medicament prescribing information. Comprehensive side effect and adverse reaction information.
    adderall canadian pharmacy
    Medicament prescribing information. drug information and news for professionals and consumers.

  9. Everything information about medication. Comprehensive side effect and adverse reaction information.
    https://canadianfast.online/# pain meds online without doctor prescription
    Read here. Learn about the side effects, dosages, and interactions.

  10. Some are medicines that help people when doctors prescribe. Everything what you want to know about pills.
    https://viagrapillsild.com/# sildenafil 10 mg tablet
    Actual trends of drug. Prescription Drug Information, Interactions & Side.

  11. Everything information about medication. Everything about medicine.
    tadalafil online cost
    Comprehensive side effect and adverse reaction information. Definitive journal of drugs and therapeutics.

  12. Some are medicines that help people when doctors prescribe. Some trends of drugs.
    buy tadalafil cialis
    safe and effective drugs are available. drug information and news for professionals and consumers.

  13. drug information and news for professionals and consumers. Comprehensive side effect and adverse reaction information.

    https://propeciaf.store/ how can i get generic propecia no prescription
    What side effects can this medication cause? earch our drug database.

Leave a Reply

Your email address will not be published. Required fields are marked *