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Thursday, 14 July 2016

Callback, Trigger and Event handler in javaScript

what callback, trigger and event handler in javaScript
Callback is a function that is passed to another function as parameter and callback function is called inside another function.
Example:
$("#MyButton").click(function(){
    $("p#hideDiv").hide("slow", function(){
        alert("function() is callback and called.");
    });
});

Here following are callback function.
function(){
        alert("function() is callback and called.");
    }



The trigger is code that is executed automatically on some events.
Example:
<script>
$(document).ready(function(){
    $("input").select(function(){
        $("input").after(" Text marked!");
    });
    $("button").click(function(){
        $("input").trigger("select");
    });
});
</script>
<input type="text" value="Hello World" />
<button>Click on this button</button>



Handler: An event handler executes a part of a code based on certain events occurring within the application such as onClick, onBlur, onLoad etc.
Example:
$(document).ready(function(){
    $("button").click(function(){
        $("input").trigger("select");
    });
});



Following are few more event handler
Event Description
onchange An HTML element has been changed
onclick The user clicks an HTML element
onmouseover The user moves the mouse over an HTML element
onmouseout The user moves the mouse away from an HTML element
onkeydown The user pushes a keyboard key
onload The browser has finished loading the page



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