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Javascript MouseEvent Tutorial with Examples

  1. MouseEvent
  2. Properties & Methods

1. MouseEvent

MouseEvent is an interface that represents for the events occurring when users interact with pointing devices, such as mouse, common events such as click, dbclick, mousedown, mouseup,...
MouseEvent is an sub-interface of UIEvent.
Event types of MouseEvent:
Event
Description
click
The event occurs when the user clicks on an element
contextmenu
The event occurs when the user right-clicks on an element to open a context menu
dblclick
The event occurs when the user double-clicks on an element
mousedown
The event occurs when the user presses a mouse button over an element
mouseup
The event occurs when a user releases a mouse button over an element
mouseenter
The event occurs when the pointer is moved onto an element
mouseleave
The event occurs when the pointer is moved out of an element
mousemove
The event occurs when the pointer is moving while it is over an element or its children.
mouseout
The event occurs when a user moves the mouse pointer out of an element, or out of one of its children
mouseover
The event occurs when the pointer is moved onto an element, or onto one of its children
mousedown, mouseup, click
Let's start with the most common event out of the mouse events that is click. It is formed from pressing down and releasing. The click event is illustrated as below:
dbclick
If you click 2 times quickly, it will create a dbclick event.
mouseover vs mouseenter
The mouseenter event occurs when the cursor enters an element. The mouseover event occurs when the cursor enters an element or one of its child elements.
mouseleave vs mouseout
The mouseleave element occurs when the cursor moves out of an element. The mouseout event happens when the cursor moves out of an element or one of its child elements.
The following example helps you compare mouseenter vs mouseover, mouseleave vs mouseout:
enter-vs-over-leave-vs-out.html
<!DOCTYPE html>
<html>

<head>
    <title>Javascript Mouse Events</title>

    <script src="enter-vs-over-leave-vs-out.js"></script>
    <style>
        #target-div {
            width: 320px;
            height: 150px;
            background: blue;
        }
        #target-div > div  {
            width: 50px;
            height: 80px;
            margin: 40px 0 0 40px;
            padding: 5px 0 0 5px;
            float: left;
            background: yellow;
        }
    </style>
</head>

<body>

    <h3>mouseenter vs mouseover</h3>
    <h3>mouseleave vs mouseout</h3>

    <div id="target-div"
               onmouseenter="mouseenterHandler(event)"
               onmouseover="mouseoverHandler(event)"
               onmouseleave="mouseleaveHandler(event)"
               onmouseout="mouseoutHandler(event)"
               >
            <div>Child</div>
            <div>Child</div>
            <div>Child</div>
    </div>
    <h3>Statistics:</h3>
    <div style="color:red;" id="statistics-div">

    </div>

</body>
</html>
enter-vs-over-leave-vs-out.js
var enterCount = 0;
var overCount = 0;

var leaveCount = 0;
var outCount = 0;


function mouseenterHandler(evt) {
    enterCount += 1;
    showStatistics();
}

function mouseoverHandler(evt) {
    overCount += 1;

    showStatistics();
}


function mouseleaveHandler(evt) {
    leaveCount += 1;
    
    showStatistics();
}

function mouseoutHandler(evt) {
    outCount += 1;

    showStatistics();
}


function showStatistics() {
    var html =
        "enterCount:" + enterCount + "<br/>" //
        +
        "overCount:" + overCount  + "<hr/>" //
        +
        "leaveCount:" + leaveCount + "<br/>" //
        +
        "outCount:" + outCount ;
    document.getElementById("statistics-div").innerHTML = html;
}
mousemove
mousemove-example.html
<!DOCTYPE html>
<html>

<head>
    <title>Javascript Mouse Events</title>

    <script src="mousemove-example.js"></script>
    <style>
        #target-div {
            width: 320px;
            height: 150px;
            background: blue;
            margin-bottom: 50px;
        }
        #target-div > div  {
            width: 50px;
            height: 150px;
            margin: 40px 0 0 40px;
            padding: 5px 0 0 5px;
            float: left;
            background: yellow;
        }
    </style>
</head>

<body>

    <h3>mousemove example</h3>

    <div id="target-div" onmousemove="mousemoveHandler(event)">

            <div>Child</div>
            <div>Child</div>
            <div>Child</div>

    </div>

    <h3>Statistics:</h3>
    <div style="color:red;" id="statistics-div">

    </div>

</body>
</html>
mousemove-example.js
var moveCount = 0;


function mousemoveHandler(evt) {
    moveCount += 1;
    showStatistics();
}


function showStatistics() {
    var html = "moveCount:" + moveCount;
    document.getElementById("statistics-div").innerHTML = html;
}

2. Properties & Methods

MouseEvent is the sub- interface of UIEvent, therefore, it inherits the properties and methods from this interface.
  • Javascript UiEvent
key
Property
Description
altKey
Returns true if "ALT" key was pressed when the mouse event was triggered, otherwise returns false.
ctrlKey
Returns true if "CTRL" key was pressed when the mouse event was triggered, otherwise returns false.
shiftKey
Returns true if "SHIFT" key was pressed when an event was triggered, otherwise returns false.
metaKey
Returns true if "META" key was pressed when an event was triggered, otherwise returns false.
Example with the ctrlKey property:
prop-ctrlKey-example.html
<!DOCTYPE html>
<html>

<head>
    <title>Javascript Mouse Events</title>

    <style>
        #target-div {
            width: 320px;
            height: 150px;
            background: blue;
            margin-bottom: 10px;
        }
    </style>
    
    <script>
      function clickHandler(evt) {
        var html = "evt.ctrlKey=" + evt.ctrlKey;

        document.getElementById("log-div").innerHTML = html;
      }
    </script>
</head>

<body>

    <h3>Press Ctrl key and Click</h3>

    <div id="target-div" onclick="clickHandler(event)" >

    </div>

    <div style="color:red;" id="log-div">

    </div>

</body>
</html>
Position:
Property
Description
clientX
Returns the horizontal coordinate of the mouse pointer, relative to the current window.
clientY
Returns the vertical coordinate of the mouse pointer, relative to the current window.
offsetX
Returns the horizontal coordinate of the mouse pointer relative to the position of the edge of the target element
offsetY
Returns the vertical coordinate of the mouse pointer relative to the position of the edge of the target element
pageX
Returns the horizontal coordinate of the mouse pointer, relative to the document.
pageY
Returns the vertical coordinate of the mouse pointer, relative to the document.
screenX
Returns the horizontal coordinate of the mouse pointer, relative to the screen (Computer or device)
screenY
Returns the vertical coordinate of the mouse pointer, relative to the screen (Computer or device)
movementX
Returns the horizontal coordinate of the mouse pointer relative to the position of the last mousemove event
movementY
Returns the vertical coordinate of the mouse pointer relative to the position of the last mousemove event
prop-positions-example.html
<!DOCTYPE html>
<html>

<head>
    <title>Javascript Mouse Events</title>

    <script src="prop-positions-example.js"></script>
    <style>
        #target-div {
            width: 300px;
            height: 210px;
            background: #ccc;
            margin: 0px 0px 10px 20px;
            padding: 5px;
        }
    </style>

</head>

<body style="height:450px; width:1000px;">

    <h3>Positions</h3>

    <div id="target-div" onmousemove="mousemoveHandler(event)" >

    </div>

</body>
</html>
prop-positions-example.js
function mousemoveHandler(evt) {

     var html =  "offsetX = " + evt.offsetX +"<br/>"
               + "offsetY = " + evt.offsetY +"<br/>"
               + "clientX = " + evt.clientX +"<br/>"
               + "clientY = " + evt.clientY +"<br/>"
               + "pageX = " + evt.pageX +"<br/>"
               + "pageY = " + evt.pageY +"<br/>"
               + "screenX = " + evt.screenX +"<br/>"
               + "screenY = " + evt.screenY +"<br/>"
               + "movementX = " + evt.movementX +"<br/>"
               + "movementY = " + evt.movementY;

      document.getElementById("target-div").innerHTML = html;
}
button
Property
Description
button
Returns a number that describes which mouse button was pressed when the mouse event was triggered
buttons
Returns a number that describes which mouse buttons were pressed when the mouse event was triggered
which
(Not a standard property, should not be used).
event.button:
  • 0: Main button, usually the left button or the un-initialized state
  • 1: Auxiliary button, usually the wheel button or the middle button (if present)
  • 2: Secondary button, usually the right button
  • 3: Fourth button, typically the Browser Back button
  • 4: Fifth button, typically the Browser Forward button
event.buttons:
  • 0 : No button or un-initialized
  • 1 : Primary button, usually the left button.
  • 2 : Secondary button, usually the right button.
  • 4 : Auxilary button, usually the mouse wheel button or middle button.
  • 8 : 4th button, typically the "Browser Back" button.
  • 16 : 5th button, typically the "Browser Forward" button.
event.buttons may return a different value other than the above values. For example, event.buttons returns 3 if you press both the left mouse and right mouse at the same time.
prop-button-buttons-example.html
<!DOCTYPE html>
<html>
   <head>
      <title>MouseEvent Example</title>

      <script>
          function mousedownHandler(evt) {
            var logDiv = document.getElementById("log-div");

            logDiv.innerHTML = "event.button= " + evt.button +"<br/>"
                             + "event.buttons= "+ evt.buttons;
          }
      </script>

   </head>
   <body>

      <h3>event.button, event.buttons</h3>

      <button onmousedown="mousedownHandler(event)">Click Me!</button>
      <br/><br/>

      <div id="log-div" style="color:red;"></div>
   </body>
</html>
Other properties
Property
Description
relatedTarget
Returns the element related to the element that triggered the mouse event

ECMAScript, Javascript Tutorials

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