7.3 transition | update pattern

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<html>
<head>

<link href="https://fonts.googleapis.com/css2?family=Montserrat+Alternates:ital,wght@0,100;0,200;0,300;0,400;0,500;0,600;0,700;0,800;0,900;1,100;1,200;1,300;1,400;1,500;1,600;1,700;1,800;1,900&family=Montserrat:ital,wght@0,100;0,200;0,300;0,400;0,500;0,600;0,700;0,800;0,900;1,100;1,200;1,300;1,400;1,500;1,600;1,700;1,800;1,900&family=Roboto:ital,wght@0,100;0,300;1,100;1,300&display=swap" rel="stylesheet">

<script src="https://d3js.org/d3.v3.min.js"></script>

<p id="h1">TRANSITION | UPDATE PATTERN </p>
<div id="link">by
<a href="https://slides.com/sandravizmad">SANDRA</a></div>

<style>

/*Defining text stylings*/

#h1 {
  font-size:30px;
  margin:30px 0px 0px 20px;
  color:#f5fa91;
  font-family: 'Montserrat Alternates', sans-serif;
  font-weight:300;
}

#link {
	font-family:'Montserrat Alternates', sans-serif;
  font-weight:200;
  font-size:10px;
	margin:5px 0px 0px 22px;
  color:white;
}

a:link, a:visited, a:active {
	text-decoration: none;
  color:white;
  border-bottom:1.5px dotted white;
}

body {
  background-color:#011227;
}

/*Defining chart stylings*/

circle {
  opacity:0.8;
}

</style>
</head>

//Margin conventions
var m = {top:100, right:50, bottom:50, left:100}
    w = 600 - m.left - m.right,
    h = 600 - m.top - m.bottom;

//Container
var svg = d3.select("body")
    .append("svg")
    .attr("width", w + m.left + m.right)
    .attr("height", h + m.top + m.bottom)
    .append("g")
    .attr("transform", `translate(${m.left}, ${m.top})`);

//X scale
var x = d3.scale.ordinal()
    .domain([0, 10, 120, 60])
    .rangePoints([0, 200], 0.9);

//Draw the circles
var circle  =svg.selectAll("circle")
  	.data([0, 10, 120, 60])
 		.enter()
		.append("circle")
   	.attr("r", 10)
   	.attr("cx", x)
    .attr("cy", h/4)
		.style("fill", "white");

setTimeout(function() {

//New data binding
    circle = circle
             .data([0, 1, 2, 3, 4], d => d);

//Style transition
    circle.transition()
             .duration(1000)
             .attr("r", 120)
             .style("fill", "#f5fa91");

//Handeling new circles
    circle.enter()
            .append("circle")
            .attr("r", 80)
            .attr("cx", 30)
            .attr("cy", h/4)
          	.style("fill", "#85f6fa");

//Handeling exiting circles
    circle.exit()
        	 .transition()
           .duration(2000)
           .style("fill", "WHITE")
           .attr("r", 60)
           .remove();

}, 1000);

</script>
</body>
</html>

https://d3js.org/d3.v3.min.js