javascript - How to remove existing nodes in d3.js -

have visit add , remove nodes in d3js don't solve problem.

there nodes @ first time, want add nodes dynamically , want if node exists update nodes , don't duplicate.

now making duplicate not updating existing ones.
here main code , full code , working fiddle here

//handles node elements var circles = svg.selectall('g');   //update graph (called when needed) function restart() {  /***************************************     draw circles (nodes) ****************************************/   circles = circles.data(data.nodes);  var g = circles.enter()                .append("g")                .attr("class", "gnode")                .attr("cursor", "pointer")                .attr("transform", function(d) { return "translate(" + d.x + "," + d.y + ")"; })                .call(force.drag);    g.append("circle")                       .attr({      "class": "node",       "cx": function(d) { return rscale(d.numoccurrences); },      "cy": function(d) { return rscale(d.numoccurrences); },      "r": function(d) { return rscale(d.numoccurrences); }  })               .style("fill", function(d, i) { return colors(i); })  .style("stroke", "#000");     g.append("text") .attr({     "x": function(d) { return rscale(d.numoccurrences); },     "y": function(d) { return rscale(d.numoccurrences); },     "font-family": "sans-serif",     "font-size": "20px",     "fill": "black",     "text-anchor": "middle"    })    .text( function (d) { return d.name; });     g.append("title")             .text(function(d) { return d.name; });   // remove old nodes  circles.exit().remove();   // set graph in motion  force.start();  }  // app starts here restart();    function dynamicaddnodes() {  var updatedata = {"name":"ios","numoccurrences":"500","color":"green","x":0,"y":1}  data.nodes.push(updatedata);      restart();  }   setinterval(dynamicaddnodes, 10000); 

try it:

circles = circles.data(data.nodes,function (d) {      return d.id;    }); 

that node's id unique.

you can see : jsfiddle.net/mohsenmhs/5r62n/