Karate Club-Question 3

<!DOCTYPE html>
<meta charset="utf-8">
<style>

.node {
  stroke: #fff;
  stroke-width: 1.5px;
}

.link {
  stroke: #999;
  stroke-opacity: .6;
}

</style>
<body>
<script src="//d3js.org/d3.v3.min.js"></script>
<h2>Zachary's Karate Problem.</h2>

Please select to see before or after split<select id="options">
<option value="option1" selected="selected">No Split</option>
<option value="option2">Split</option>
<input type="submit" onclick="myFunction()">
</select >

var color = d3.scale.category20();

var force = d3.layout.force()
    .charge(-120)
    .linkDistance(30)
    .size([width, height]);

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

d3.json("output1.json", function(error, graph) {
  if (error) throw error;

force
      .nodes(graph.nodes)
      .links(graph.links)
      .start();

var link = svg.selectAll(".link")
      .data(graph.links)
    .enter().append("line")
      .attr("class", "link")
      //.style("stroke-width", function(d) { return Math.sqrt(d.value); });

var node = svg.selectAll(".node")
      .data(graph.nodes)
    .enter().append("circle")
      .attr("class", "node")
      .attr("r", 8)
	  
	 //.on("click", function(d){
      //.style("fill", function(d) { return color(d.faction); })
    //});
     
      .call(force.drag);

node.append("title")
      .text(function(d) { return d.name; });

force.on("tick", function() {
    link.attr("x1", function(d) { return d.source.x; })
        .attr("y1", function(d) { return d.source.y; })
        .attr("x2", function(d) { return d.target.x; })
        .attr("y2", function(d) { return d.target.y; });

node.attr("cx", function(d) { return d.x; })
        .attr("cy", function(d) { return d.y; });
  });

});
function myFunction() {
    var drop1 = document.getElementById("options");
	 
	
	var selectedValue = drop1.options[drop1.selectedIndex].value;
	if (selectedValue == "option1"){
	
	d3.selectAll(".node").style("fill", function(d) { return color(); })

}
	else{
	//d3.selectAll(".node").style("fill", function(d) { return color(d.faction); })
	
	d3.selectAll(".node").style("fill", function(d) { return color(d.faction); })
	}
   
}

</script>

</body>

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