AJAX Basics and JSON Examples
This content covers the basics of AJAX, XMLHttpRequest, handling responses, JSON examples, and JavaScript code for parsing JSON data. It also includes a JSON output example, AJAX responses, and controller code for handling JSON data in web development.
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Presentation Transcript
AJAX Basics xhr = new XMLHttpRequest(); xhr.onreadystatechange = xhrHandler; xhr.open("POST", url); xhr.send(postData); ... function xhrHandler() { if (this.readyState != 4) { return; } if (this.status != 200) { // Handle error ... return; } ... var text = this.responseText; } State 4 means done Raw text of response (also available as XML) CS 142 Lecture Notes: Ajax Slide 1
JSON {name: "Alice", gpa: 3.5, friends: ["Bill", "Carol", "David"]} CS 142 Lecture Notes: Ajax Slide 2
JSON Example Controller code: Class StudentsController < ApplicationController def get_students @students = Student.all render json: @students end end [{"advisor_id":"2","birth":"1987-10-22", "gpa":3.9,"grad":2009,"id":1, "name":"Anderson"}, {"advisor_id":"1","birth":"1990-04-16", "gpa":3.1,"grad":2012,"id":2, "name":"Jones"}, ... ] JSON Output Javascript in browser: var students = JSON.parse(xhr.responseText); element.innerHTML = students[1].name; AJAX response (from XMLHttpRequest object) Slide 3
CS 142 Lecture Notes: Cookies Slide 4
