beginner node.js callback example [closed] - node.js

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I'm pretty novice in nodejs
This is a very easy php example that I want to write in nodejs
$key='foo';
$inside= openthedoor($key);
if(!$inside){ //wrong key
$key= getanewkey();//get a new key
$inside= openthedoor($key);//open the door again
}
How can I do this callback in nodejs?
appologies for the stupid question.

Answer 1

Keep in mind that you can still write things synchronously in Node.js, but if openthedoor() did happen to require a callback function, this is what it'd look like:
var key = 'foo';
openthedoor(key, function(inside) {
if (!inside) {
key = getanewkey();
openthedoor(key, function(inside) {
// check if we're inside again
});
}
});
A callback function is a function that is called on completion of another function. In the example, you are passing this function:
var callback = function(inside) {
if (!inside) {
// do something else
}
});
Into this function to be called when there is a result:
openthedoor(key, callback);