sync vs async js code example

Example 1: async vs sync

synchronous (sync) - you can only execute one thing at a time
asynchronous (async) - you can execute multiple things at the same time

Example 2: synchronous vs asynchronous functions javascript

// Example 1 - Synchronous (blocks)
var result = database.query("SELECT * FROM hugetable");
console.log("Query finished");
console.log("Next line");


// Example 2 - Asynchronous (doesn't block) 
database.query("SELECT * FROM hugetable", function(result) {
    console.log("Query finished");
});
console.log("Next line");