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Canvas Enter/Update/Exit/Transition
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<!DOCTYPE html> | |
<meta charset="utf-8"> | |
<script src="https://d3js.org/d3.v5.js"></script> | |
<body> | |
<script> | |
var canvas = d3.select("body") | |
.append("canvas") | |
.attr("width", 600) | |
.attr("height", 200); | |
var context = canvas.node().getContext("2d"); | |
var data = [1,2,3,4,5]; | |
// container for dummy elements: | |
var faux = d3.select(document.createElement("custom")); | |
// normal update exit selection with dummy elements: | |
function update() { | |
// modify data: | |
manipulateData(); | |
var selection = faux.selectAll("circle") | |
.data(data, function(d) { return d;}); | |
var exiting = selection.exit().size(); | |
var exit = selection.exit() | |
.transition() | |
.attr("r",0) | |
.attr("cy", 70) | |
.attr("fill","white") | |
.duration(1200) | |
.remove(); | |
var enter = selection.enter() | |
.append("circle") | |
.attr("cx", function(d,i) { | |
return (i + exiting) * 20 + 20; | |
}) | |
.attr("cy", 50) | |
.attr("r", 0) | |
.attr("fill",function(d) { return ["orange","steelblue","crimson","violet","yellow"][d%5]; }); | |
enter.transition() | |
.attr("r", 8) | |
.attr("cx", function(d,i) { | |
return i * 20 + 20; | |
}) | |
.duration(1200); | |
selection | |
.transition() | |
.attr("cx", function(d,i) { | |
return i * 20 + 20; | |
}) | |
.duration(1200); | |
} | |
// update every 1.2 seconds | |
setInterval(update,1200); | |
// rendering function, called repeatedly: | |
function render() { | |
context.clearRect(0, 0, 600, 200); | |
faux.selectAll("circle").each(function() { | |
var sel = d3.select(this); | |
context.beginPath(); | |
context.arc(sel.attr("cx"),sel.attr("cy"),sel.attr("r"),0,2*Math.PI); | |
context.fillStyle = sel.attr("fill"); | |
context.fill(); | |
context.stroke(); | |
}) | |
window.requestAnimationFrame(render) | |
} | |
window.requestAnimationFrame(render) | |
// to manipulate data: | |
var index = 6; // to keep track of elements. | |
function manipulateData() { | |
data.forEach(function(d,i) { | |
var r = Math.random(); | |
if (r < 0.5 && data.length > 1) { | |
data.splice(i,1); | |
} | |
else { | |
data.push(index++); | |
} | |
}) | |
} | |
</script> |
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