javascript callback
/*
A callback function is a function passed into another function
as an argument, which is then invoked inside the outer function
to complete some kind of routine or action.
*/
function greeting(name) {
alert('Hello ' + name);
}
function processUserInput(callback) {
var name = prompt('Please enter your name.');
callback(name);
}
processUserInput(greeting);
// The above example is a synchronous callback, as it is executed immediately.callback function js
function greeting(name) {
alert('Hello ' + name);
}
function processUserInput(callback) {
var name = prompt('Please enter your name.');
callback(name);
}
processUserInput(greeting);how to make callback function javascript
function startWith(message, callback){
console.log("Clearly written messages is: " + message);
//check if the callback variable is a function..
if(typeof callback == "function"){
callback(); //execute function if function is truly a function.
}
}
//finally execute function at the end
startWith("This Messsage", function mySpecialCallback(){
console.log("Message from callback function");
})create callback function javascript
function add(a, b, callback) {
if (callback && typeof(callback) === "function") {
callback(a + b);
}
}
add(5, 3, function(answer) {
console.log(answer);
});javascript callback function
// Callback Example 1: note, fn=function
/*
In JavaScript, callback fn is:
- a function based into another functions as an argument to be
executed LATER
- would be a Synchronous OR Asynchronous callback.
- hint:
Synchronous: processing from top to bottom,
stop until current code finished.
Asynchronous: no wait, process the next block if there
*/
let numbers = [1, 2, 4, 7, 3, 5, 6];
/* To find all the odd numbers in the array,
you can use the filter() method of the Array object.
- The filter() method creates a new array with the elements that
pass the test implemented by a fn.
- The following test fn returns true if a number is an odd
number: */
function isOddNumber(number) { //to be the callback fn
return number % 2;
}
// callback fn passed into another fn by its reference, No ()
const oddNumbers = numbers.filter(isOddNumber);
console.log(oddNumbers); // [ 1, 7, 3, 5 ]javascript callback function
const message = function() {
console.log("This message is shown after 3 seconds");
}
setTimeout(message, 3000);Copyright © 2021 Codeinu
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