SVG + JavaScript
SVG can be used together with JavaScript to modify and animate SVG elements.
SVG Simple Script
In this example, we create a red circle with a radius of 25. Click the button to change the radius to 50:
Here is the SVG code:
Example
<svg width="200" height="100" xmlns="http://www.w3.org/2000/svg">
<circle id="circle1" cx="50" cy="50" r="25" style="fill:red;" />
</svg>
<input type="button" value="Change Radius" onclick="changeRadius()" />
<script>
function changeRadius() {
document.getElementById("circle1").setAttribute("r", "50");
}
</script>
Code explanation:
- Add an
idattribute to the<circle>element - Create a script within
<script>tags - Get a reference to the SVG element with the
getElementById()function - Change the
rattribute using thesetAttribute()function - Add an
<input type="button">element to run the JavaScript when clicked
SVG Change CSS
In this example, we create a red circle. Click the button to change the fill color to green:
Here is the SVG code:
Example
<svg width="200" height="100" xmlns="http://www.w3.org/2000/svg">
<circle id="circle2" cx="50" cy="50" r="25" style="fill:red;" />
Sorry, your browser does not support inline SVG.
</svg>
<input type="button" value="Change Style" onclick="changeStyle()" />
<script>
function changeStyle() {
document.getElementById("circle2").style.fill="green";
}
</script>
Code explanation:
- Add an
idattribute to the<circle>element - Create a script within
<script>tags - Get a reference to the SVG element with the
getElementById()function - Set a new fill color with
style.fill - Add an
<input type="button">element to run the JavaScript when clicked
SVG Change Attribute Values and CSS
In this example, we create a red circle. Click the button to change the radius, the x position, fill color, and add a stroke color:
Here is the SVG code:
Example
<svg width="200" height="120" xmlns="http://www.w3.org/2000/svg">
<circle id="circle3" cx="50" cy="60" r="25" style="fill:red;" />
</svg>
<input type="button" value="Change Circle" onclick="changeMe()" />
<script>
function changeMe() {
var c = document.getElementById("circle3");
c.setAttribute("r", "50");
c.setAttribute("cx", "150");
c.style.fill="green";
c.style.stroke="red";
}
</script>
SVG Script for Animation
In this example, we create a red circle. Click the two buttons to start and stop the animation:
Here is the SVG code:
Example
<svg width="600" height="100" xmlns="http://www.w3.org/2000/svg">
<circle id="circle4" cx="50" cy="50" r="50" style="fill:red;" />
</svg>
<script>
var t = null;
function start() {
if(t == null) {
t = setInterval(animate, 20);
}
}
function stop() {
if(t != null) {
clearInterval(t);
t = null;
}
}
function animate() {
var circle = document.getElementById("circle4");
var cx = circle.getAttribute("cx");
var newCX = 2 + parseInt(cx);
if(newCX > 600) {
newCX = 50;
}
circle.setAttribute("cx", newCX);
}
</script>
<br/>
<input type="button" value="Start" onclick="start()" />
<input type="button" value="Stop" onclick="stop()" />
Code explanation:
- The
start()andstop()functions start and stop the animation - The animation starts by setting up a timer (t) which calls the
animate()function every 20 milliseconds with thesetInterval()function - The animation is stopped by clearing the t timer
- The animation is performed inside the
animate()function - Get a reference to the
<circle>element with thegetElementById()function - Get the value of the
cxattribute with thegetAttribute()function - Convert the value of the
cxattribute to a number withparseInt(). Then add 2 to thecxvalue - Test if the
newCXvalue is larger than 600 (which is the width of the SVG "window"), then reset it to 50 (which is the original start position) - Put the
newCXvalue into thecxattribute of the<circle>element with thesetAttribute()function. This moves the circle to the new cx-position
