Question

Hi all please let me know the meaning of following statement

addEvent(window, 'storage', function (event){
    if (event.key == 'storage-event-test'){
        output.innerHTML = event.newValue;
    }
});

addEvent(dataInput, 'keyup', function (){
    localStorage.setItem('storage-event-test', this.value);
});

Please explain me what is addEvent() method and what does above code does.

Answer 1

There is no addEvent method as part of javascript, could be an externally written function. There is element.addEventListener

From your code the addEvent expects this signature:

addEvent(obj, an_event_string, callback_fn);

The first parameter I’m not sure about, just takes an object. The second is a string representing (I’m guessing) the event and the third is a function that is called when the event happens.

addEvent(window, 'storage', function (event){
    //for the "storage" event this function is called
   // and some info is passed in the event argument
    if (event.key == 'storage-event-test'){ //if the key is..
        output.innerHTML = event.newValue;
    }//then set the innerHtml to a value from the event
});

addEvent(dataInput, 'keyup', function (){
    //for the "keyup" event
    //save an item into local storage
    localStorage.setItem('storage-event-test', this.value);
});

See here for more about local storage.