Element: mousemove event
Baseline
Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.
The mousemove event is fired at an element when a pointing device (usually a mouse) is moved while the cursor's hotspot is inside it.
These events happen whether or not any mouse buttons are pressed. They can fire at a very high rate, depends on how fast the user moves the mouse, how fast the machine is, what other tasks and processes are happening, etc.
Syntax
Use the event name in methods like addEventListener(), or set an event handler property.
addEventListener("mousemove", (event) => { })
onmousemove = (event) => { }
Event type
A MouseEvent. Inherits from UIEvent and Event.
Examples
The following example uses the mousedown, mousemove, and mouseup events to allow the user to draw on an HTML canvas. Its functionality is simple: the thickness of the line is set to 1, and the color is always black.
When the page loads, constants myPics and context are created to store a reference to the canvas and the 2d context we will use to draw.
Drawing begins when the mousedown event fires. First we store the x and y coordinates of the mouse pointer in the variables x and y, and then set isDrawing to true.
As the mouse moves over the page, the mousemove event fires. If isDrawing is true, the event handler calls the drawLine function to draw a line from the stored x and y values to the current location.
When the drawLine() function returns, we adjust the coordinates and then save them in x and y.
The mouseup event draws the final line segment, sets x and y to 0, and stops further drawing by setting isDrawing to false.
HTML
<h1>Drawing with mouse events</h1>
<canvas id="myPics" width="560" height="360"></canvas>
CSS
canvas {
border: 1px solid black;
width: 560px;
height: 360px;
}
JavaScript
// When true, moving the mouse draws on the canvas
let isDrawing = false;
let x = 0;
let y = 0;
const myPics = document.getElementById("myPics");
const context = myPics.getContext("2d");
// event.offsetX, event.offsetY gives the (x,y) offset from the edge of the canvas.
// Add the event listeners for mousedown, mousemove, and mouseup
myPics.addEventListener("mousedown", (e) => {
x = e.offsetX;
y = e.offsetY;
isDrawing = true;
});
myPics.addEventListener("mousemove", (e) => {
if (isDrawing) {
drawLine(context, x, y, e.offsetX, e.offsetY);
x = e.offsetX;
y = e.offsetY;
}
});
window.addEventListener("mouseup", (e) => {
if (isDrawing) {
drawLine(context, x, y, e.offsetX, e.offsetY);
x = 0;
y = 0;
isDrawing = false;
}
});
function drawLine(context, x1, y1, x2, y2) {
context.beginPath();
context.strokeStyle = "black";
context.lineWidth = 1;
context.moveTo(x1, y1);
context.lineTo(x2, y2);
context.stroke();
context.closePath();
}
Result
Specifications
| Specification |
|---|
| Pointer Events # mousemove |
| HTML # handler-onmousemove |