Jagathishrex

"use strict";
let user = { name : "Jagathish" };
Object.isExtensible(user); // true

Object.preventExtensions(user);

Object.isExtensible(user); // false

Jagathishrex

"use strict";
let user = { name : "Jagathish" };

Object.preventExtensions(user);

try {
  user.age = 23;
} catch (e) {
  console.log(e);
  // expected output: TypeError:Cannot add property age, object is not extensible

Jagathishrex

"use strict";
let user = {
  name : "Jagathish",
  age : 23,
  mobile : 123123123,
  address : "221B Baker Stree, London"
};

let handler = {
  set(target, prop, val){

Jagathishrex

| Number | Rider | Time | | 1 | Bullet Bob | 56:07 | | 2 | Clumsy Colin | DNF | | 3 | Swift Susan | 55:13 |

Jagathishrex

let target = {};
let handler = {}; // empty handler
let proxy = new Proxy(target, handler); 

proxy.test = 5; // the property will be added in target

target.test; // 5
proxy.test; // 5 

Jagathishrex

let target = {
  name : "Mia",
  age : 28
};
let handler = {
  get(targetObject, propertyName) {
     if( propertyName in targetObject) { 
        return `The ${propertyName} is ${targetObject[propertyName]}`;
      }
  }

Jagathishrex

let fileInput = document.getElementById('file_chooser');

fileInput.addEventListener('change', function(e) {
  
  var file = this.files[0];
  var fd = new FormData();
  fd.append("file", file);
  
  var request = new XMLHttpRequest();
  request.open('POST', 'http:myserver.com/upload');

Jagathishrex

let fileInput = document.getElementById('file_chooser');

fileInput.addEventListener('change', function(e) {
  
  var file = this.files[0];
  var fd = new FormData();
  fd.append("file", file);
  
  var request = new XMLHttpRequest();
  request.open('POST', 'http:myserver.com/upload');

Jagathishrex

let url = "https://medium.com/search?q=javascriptjeep";
let request = new XMLHttpRequest();
console.log(request.readyState); // 0
//after calling open the state will be changed to 1

request.open("GET", url);
console.log(request.readyState); // 1

// we need to implement readystatechange event to detect 2,3,4, events
request.onreadystatechange = function() {

Jagathishrex

request.onprogress = function(e) { // triggers periodically 
  /* 
    e.loaded - how many bytes downloaded
    e.lengthComputable = true if the server sent Content-Length header, if true we can find the size of the response  
    e.total - total number of bytes (if lengthComputable is true)
   */
    let total = e.lengthComputable ? e.total : 0;
    let loaded = e.loaded;
  
    if(total) {