D3 Examples - The Best Bar Chart Ever Updating

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<!DOCTYPE html>
<head>
  <meta charset="utf-8">
  <script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.17/d3.js"></script>
  <style>
    body { margin:0;position:fixed;top:0;right:0;bottom:0;left:0; }
    
    .axis path,
    .axis line {
      fill: none;
      stroke: #000;
      shape-rendering: crispEdges;
    }
​
    .bar {
      fill: steelblue;
    }
​
   
  </style>
</head>
​
<body>
    <script>
    //var = [1,2,3,4,5]
    
    var data = [{x: "A", y: 10, color: "green"},{x: "B", y: 12, color: "orange"},{x: "C", y: 10, color: "green"},{x: "D", y: 9, color: "red"}];
    
    
    var margin={top: 20, right: 30, bottom: 30, left: 30};
    
    var width = 960 - margin.left -margin.right;
    var height = 500 - margin.top - margin.bottom;
    
    var svg = d3.select("body").append("svg")
        .attr({
        width: width + margin.left + margin.right,
        height: height + margin.top + margin.bottom
      });
        //.style("background-color", "green")
    
    var g = svg.append("g")
            .attr("transform", "translate(" + margin.left + "," + margin.top + ")");
    
    var axis_x = d3.scale.ordinal().rangeRoundBands([0, width], 0.1, 0.2);
    
    var axis_y = d3.scale.linear().range([height, 0]);    
    
    function draw(newData){
            d3.selectAll(".axis").remove();
      axis_y.domain([0, d3.max(newData.map(function(d){return d.y}))]);
      axis_x.domain(newData.map(function(d){ return d.x}));
      
       g.append("g")
         .attr("class", "y axis")
         .call(d3.svg.axis().scale(axis_y).orient("left"));
​
       g.append("g")
         .attr("class", "x axis")
         .attr("transform", "translate(0," + height + ")")
         .call(d3.svg.axis().scale(axis_x).orient("bottom"));
​
       //SELECTION
​
       var bars = g.selectAll(".bar").data(newData);
​
      //ENTERING
      var barEntering = bars.enter()
        .append("rect")
        .attr("class", "bar");
​
      //ATTRIBUTES
      bars
      .attr({
        x: function(d){ return axis_x(d.x)},
                //y: function(d){ return axis_y(d.y)},
        width: axis_x.rangeBand(),
       // height: function(d){ return height - axis_y(d.y)}
      })
      .transition()
      .duration(500)
      .attr({
        y: function(d){ return axis_y(d.y)},
        height: function(d){ return height - axis_y(d.y)}
      });
​
​
      //EXITING
      var barsExiting = bars.exit().remove(); 
    }
​
    
    setInterval(function(){
      draw([{x: "A", y: Math.random()*10, color: "green"},{x: "B", y: Math.random()*10, color: "orange"},{x: "C", y: Math.random()*10, color: "green"},{x: "D", y: Math.random()*10, color: "red"}])
    }, 1000)
    
  </script>
</body>
​
    