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JSON

JSON. 2017, Fall Pusan National University Ki-Joune Li. JSON – Basic Concepts. Browser. Web Server. JavaScript Object. JSON. From JavaScript Object to JSON.

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JSON

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  1. JSON 2017, Fall Pusan National University Ki-Joune Li

  2. JSON – Basic Concepts Browser Web Server JavaScript Object JSON From JavaScript Object to JSON var myObj ={ "name":"John", "age":31, "city":"New York" };var myJSON = JSON.stringify(myObj);window.location = "demo_json.php?x=" + myJSON; From JSON Object to JavaScript var myJSON ='{ "name":"John", "age":31, "city":"New York" }';var myObj = JSON.parse(myJSON);document.getElementById("demo").innerHTML = myObj.name; • JSON (JavaScript Object Notation) • A Format (or Syntax) to store and exchange object data • Text data

  3. JSON – Basic Concepts JavaScript Program JavaScript Object JSON Local Storage Storing data: myObj = { "name":"John", "age":31, "city":"New York" };myJSON = JSON.stringify(myObj);localStorage.setItem("testJSON", myJSON); Reading data text = localStorage.getItem("testJSON");obj = JSON.parse(text);document.getElementById("demo").innerHTML = obj.name; • JSON (JavaScript Object Notation) • Storing data in local storage as text data

  4. Syntax { "name":"John",  "age":30,  "car":null } var person = { "name":"John", "age":31, "city":"New York" }; var x=person.name; var y=person["name"]; // named index var person["name"]="Guilbert"; • Use JavaScript Syntax • Data is in name/value pairs • Data is separated by commas • Curly braces hold objects • Square brackets hold arrays • JSON object in JavaScript • JSON object is accessible in JavaScript

  5. JSON – Data Types and Values • JSON values must be one of the following types • a string (should be always doubl-quoted): {"name":"John" } • a number:  {"name":"John" } • an object (JSON object): { "employee":{"name":"John", "age":30, "city":"New York" } } • an array: {"employees":[ "John", "Anna", "Peter" ] } • a boolean: {“married”:true} • null: { “middlename”: null} • JSON file: .json

  6. JSON – Object myObj ={ "name":"John", "age":30, "car":null };x = myObj.name; x = myObj["name"]; myObj ={ "name":"John", "age":30, "car":null };for (x in myObj) {    document.getElementById("demo").innerHTML += myObj[x] + "<br>"; } • JSON Object • JSON objects are surrounded by curly braces {}. • JSON objects are written in key/value pairs. • Keys must be strings, and values must be a valid JSON data type (string, number, object, array, boolean or null). • Keys and values are separated by a colon. • Each key/value pair is separated by a comma. • Accessing JSON Object within JavaScript

  7. JSON – Object myObj ={ "name":"John","age":30,"cars": {"car1":"Ford","car2":"BMW","car3":"Fiat"    } } x = myObj.cars.car2;//or:x = myObj.cars["car2"]; myObj.cars["car2"] = "Mercedes"; delete myObj.cars.car2; • Nested JSON Objects • Values in a JSON object can be another JSON object.

  8. JSON – Object <!DOCTYPE html> <html> <body> <p>Loopin through an array using a for loop:</p> <p id="demo"></p> <script> var myObj, i, x = ""; myObj = { "name":"John", "age":30, "cars":[ "Ford", "BMW", "Fiat" ] }; for (i = 0; i < myObj.cars.length; i++) { x += myObj.cars[i] + "<br>"; } document.getElementById("demo").innerHTML = x; </script> </body> </html> for (i in myObj.cars) { • JSON Array Objects • Values in a JSON object can be another JSON object.

  9. JSON – Object myObj ={ "name":"John",    "age":30,"cars": [ { "name":"Ford", "models":[ "Fiesta", "Focus", "Mustang" ] },        { "name":"BMW", "models":[ "320", "X3", "X5" ] },        { "name":"Fiat", "models":[ "500", "Panda" ] }] }

  10. JSON – Parse and Stringify var obj = { "name":"John", "age":30, "city":"New York"};var myJSON = JSON.stringify(obj); Convert JavaScript Object to JSON: Stringify Browser Web Server JavaScript Object JSON Convert JSON to JavaScript Objects: parsing var obj = JSON.parse('{ "name":"John", "age":30, "city":"New York"}');

  11. JSON – XML vs. JSON {"employees":[    { "firstName":"John", "lastName":"Doe" },    { "firstName":"Anna", "lastName":"Smith" },    { "firstName":"Peter", "lastName":"Jones" }]} <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> Both JSON and XML can be used to receive data from a web server.

  12. JSON – XML vs. JSON • JSON is like XML • Both JSON and XML are "self describing" (human readable) • Both JSON and XML are hierarchical (values within values) • Both JSON and XML can be parsed and used by lots of programming languages • Both JSON and XML can be fetched with an XMLHttpReques • JSON is unlike XML • JSON doesn't use end tag • JSON is shorter • JSON is quicker to read and write • JSON can be included within JavaScript (e.g. object, arrays) • XML has to be parsed with an XML parser. JSON can be parsed by a standard JavaScript function JSON.parse

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