What are jQuery Events? Syntax For Event Methods

What are Events?

All the different visitor's actions that a web page can respond to are called events. An event represents the precise moment when something happens.

• moving a mouse over an element
• selecting a radio button
• clicking on an element

The term "fires/fired" is often used with events. Example: "The keypress event is fired, the moment you press a key".

Here are some common DOM events:

Mouse Events	Keyboard Events	Form Events	Document/Window Events
click	keypress	submit	load
dblclick	keydown	change	resize
mouseenter	Keyup	focus	scroll
mouseleave		blur	Unload

jQuery Syntax For Event Methods

In jQuery, most DOM events have an equivalent jQuery method. To assign a click event to all paragraphs on a page, you can do this:

$("p").click();

The next step is to define what should happen when the event fires. You must pass a function to the event:

$("p").click(function(){
  // action goes here!!
});

Commonly Used jQuery Event Methods

$(document).ready()

The $(document).ready() method allows us to execute a function when the document is fully loaded.

click()

The click() method attaches an event handler function to an HTML element. The function is executed when the user clicks on the HTML element. The following example says: When a click event fires on a <p> element; hide the current <p> element:

$("p").click(function(){
   $(this).hide();
});

dblclick()

The dblclick() method attaches an event handler function to an HTML element. The function is executed when the user double-clicks on the HTML element:

$("p").dblclick(function(){
   $(this).hide();
});

mouseenter()

The mouseenter() method attaches an event handler function to an HTML element. The function is executed when the mouse pointer enters the HTML element:

$("#p1").mouseenter(function(){
    alert("You entered p1!");
});

mouseleave()

The mouseleave() method attaches an event handler function to an HTML element. The function is executed when the mouse pointer leaves the HTML element:

$("#p1").mouseleave(function(){
    alert("Bye! You now leave p1!");
});

mousedown()

The mousedown() method attaches an event handler function to an HTML element. The function is executed, when the left, middle or right mouse button is pressed down, while the mouse is over the HTML element:

$("#p1").mousedown(function(){
    alert("Mouse down over p1!");
});

mouseup()

The mouseup() method attaches an event handler function to an HTML element. The function is executed, when the left, middle or right mouse button is released, while the mouse is over the HTML element:

$("#p1").mouseup(function(){
    alert("Mouse up over p1!");
});

hover()

The hover() method takes two functions and is a combination of the mouseenter() and mouseleave() methods. The first function is executed when the mouse enters the HTML element, and the second function is executed when the mouse leaves the HTML element:

$("#p1").hover(function(){
    alert("You entered p1!");
},
function(){
    alert("Bye! You now leave p1!");
});

focus()

The focus() method attaches an event handler function to an HTML form field. The function is executed when the form field gets focus:

$("input").focus(function(){
    $(this).css("background-color", "#cccccc");
});

blur()

The blur() method attaches an event handler function to an HTML form field. The function is executed when the form field loses focus:

$("input").blur(function(){
    $(this).css("background-color", "#ffffff");
});

The on() Method

The on() method attaches one or more event handlers for the selected elements. Attach a click event to a <p> element:

$("p").on("click", function(){
    $(this).hide();
});

Attach multiple event handlers to a <p> element:

$("p").on({
    mouseenter: function(){
        $(this).css("background-color", "lightgray");
    }, 
    mouseleave: function(){
        $(this).css("background-color", "lightblue");
    }, 
    click: function(){
        $(this).css("background-color", "yellow");
    } 
});