Example of using version 4 of d3.js to drag circles around the screen. Want to learn this? Read this.
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February 16, 2021 21:41
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Dragging Circles
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<!DOCTYPE html> | |
<meta charset="utf-8"> | |
<svg width="960" height="600"></svg> | |
<script src="https://d3js.org/d3.v4.min.js"></script> | |
<script> | |
var svg = d3.select("svg"), | |
width = +svg.attr("width"), | |
height = +svg.attr("height"); | |
//create some circles at random points on the screen | |
//create 50 circles of radius 20 | |
//specify centre points randomly through the map function | |
radius = 20; | |
var circle_data = d3.range(50).map(function() { | |
return{ | |
x : Math.round(Math.random() * (width - radius*2 ) + radius), | |
y : Math.round(Math.random() * (height - radius*2 ) + radius) | |
}; | |
}); | |
//add svg circles | |
var circles = d3.select("svg") | |
.append("g") | |
.attr("class", "circles") | |
.selectAll("circle") | |
.data(circle_data) | |
.enter() | |
.append("circle") | |
.attr("cx", function(d) {return(d.x)}) | |
.attr("cy", function(d) {return(d.y)}) | |
.attr("r", radius) | |
.attr("fill", "green"); | |
//create drag handler with d3.drag() | |
//only interested in "drag" event listener, not "start" or "end" | |
var drag_handler = d3.drag() | |
.on("drag", function(d) { | |
d3.select(this) | |
.attr("cx", d.x = d3.event.x ) | |
.attr("cy", d.y = d3.event.y ); | |
}); | |
//apply the drag_handler to our circles | |
drag_handler(circles); | |
</script> |
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