javascript send method as callback code example

Example 1: javascript callback function

const message = function() {  
    console.log("This message is shown after 3 seconds");
}
 
setTimeout(message, 3000);

Example 2: how to pass callback function in javascript

function functionOne(x) { alert(x); }

function functionTwo(var1, callback) {
    callback(var1);		
}

functionTwo(2, functionOne);