JSFiddle - React, Tailwind, and code Playground

JavaScript

//Width and height
var w = 500;

var svg = d3.select("body")
.append("svg")
.attr("width", 100)
.attr("height", 100);


svg.append("rect")
.attr({x:0,y:20,height:10,width:10,fill:'red'})
.attr("sort",3);
svg.append("rect")
.attr({x:0,y:0,height:10,width:10,fill:'yellow'})
.attr("sort",2);
svg.append("rect")
.attr({x:0,y:40,height:10,width:10,fill:'blue'})
.attr("sort",1);

d3.selectAll("rect").sort(function(a,b){return a.attr("sort")-b.attr("sort")});

d3.selectAll("rect")
.each(function(d,i){alert(d3.select(this).attr("sort"))});