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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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