MouseEvent.pageX - Web APIs 编辑

The pageX read-only property of the MouseEvent interface returns the X (horizontal) coordinate (in pixels) at which the mouse was clicked, relative to the left edge of the entire document. This includes any portion of the document not currently visible.

Being based on the edge of the document as it is, this property takes into account any horizontal scrolling of the page. For example, if the page is scrolled such that 200 pixels of the left side of the document are scrolled out of view, and the mouse is clicked 100 pixels inward from the left edge of the view, the value returned by pageX will be 300.

Originally, this property was defined as a long integer. The CSSOM View Module redefined it as a double float. See the Browser compatibility section for details.

See Page in Coordinate systems for some additional information about coordinates specified in this fashion.

Syntax

var pageX = MouseEvent.pageX;

Value

A floating-point number of pixels from the left edge of the document at which the mouse was clicked, regardless of any scrolling or viewport positioning that may be in effect.

This property was originally specified in the Touch Events specification as a long integer, but was redefined in the CSSOM View Module to be a double-precision floating-point number to allow for subpixel precision. Even though numeric types both are represented by Number in JavaScript, they may be handled differently internally in the browser's code, resulting in potential behavior differences. See Browser compatibility to learn which browsers have been updated to use the revised data type.

Example

More examples

Let's take a look at a simple example that shows you the mouse's position relative to the page's origin. Since this example is presented in an <iframe>, that top-left corner is the top-left corner of the frame, not the browser window.

JavaScript

var box = document.querySelector(".box");
var pageX = document.getElementById("x");
var pageY = document.getElementById("y");

function updateDisplay(event) {
  pageX.innerText = event.pageX;
  pageY.innerText = event.pageY;
}

box.addEventListener("mousemove", updateDisplay, false);
box.addEventListener("mouseenter", updateDisplay, false);
box.addEventListener("mouseleave", updateDisplay, false);

The JavaScript code uses addEventListener() to register the function updateDisplay() as the event handler for the mousemove, mouseenter, and mouseleave events.

updateDisplay() replaces the contents of the <span> elements meant to contain the X and Y coordinates with the values of pageX and pageY.

HTML

<div class="box">
  <p>
    Move the mouse around in this box to watch its coordinates change.
  </p>
  <p>
    <code>pageX</code>: <span id="x">n/a</span>
  </p>
  <p>
    <code>pageY</code>: <span id="y">n/a</span>
  </p>
</div>

The HTML is simple; the box we'll be watching for mouse events on is given the class "box". It has two <span> elements, one with the ID "x" and one with the ID "y". Those will be updated each time an event occurs to contain the latest mouse coordinates relative to the page.

.box {
  width: 400px;
  height: 250px;
  border: 2px solid darkblue;
  background-color: blue;
  color: white;
  font: 16px "Zilla", "Open Sans", "Helvetica", "Arial", sans-serif;
}

Result

Try this out here:

Specifications

Prior to being added to the CSSOM View specification, pageX and pageY were available on the UIEvent interface in a limited subset of browsers for a short time.

Browser compatibility

BCD tables only load in the browser

See also

• MouseEvent.pageY