Asynchronous programming basics

async-basics.js

// Time elapsed: 0µs

var a = 200000000000;
for (var i = 1000; i; i--){
  a = a / 3;
}

// Time elapsed: 1µs, probably less




var exampleData = '';

$.getJSON(
  'http://example.com/data.json',
  function(data){
    
    exampleData = data;
    // Time elapsed: ~200000µs, after ajax request completes
    // Value of exampleData: { live data }
    
    // Second execution block terminates here
  })
);

// We have now fired an ajax request and registered code to execute on ajax complete
// Time elapsed: still 1µs
// Value of exampleData: ''

// Execution block terminates here