Javascript 在d3中拖动一条线

我在d3中创建了一条线，我想把它拖过来

var line = d3.select("svg")
              .append("line")
              .attr("x1",10)
              .attr("y1",10)
              .attr("x2",200)
              .attr("y2",200)
              .attr("stroke-width",10)
              .attr("stroke","black")
              .call(drag);

我现在的问题是，如何将两个点（x1，y1）（x2，y2）从相对于鼠标位置的直线上移动，因为我可能还需要dragstart鼠标位置

let drag = d3.behavior.drag()
           .on('dragstart', null)
           .on('drag', function(){
             // move circle
             let x1New = d3.select(this).attr('x1')+ ???;
             let y1New = d3.select(this).attr('y1')+ ???;
             let x2New = d3.select(this).attr('x2')+ ???;
             let y2New = d3.select(this).attr('y2')+ ???;
             line.attr("x1",x1New)
                 .attr("y1",y1New)
                 .attr("x2",x2New)
                 .attr("y2",y2New);
             })
           .on('dragend', function(){
           }); 

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我希望你能帮我做这件事。

在拖动功能中这样做：

.on('drag', function(d){
             // move circle
             var dx = d3.event.dx;//this will give the delta x moved by drag
             var dy = d3.event.dy;//this will give the delta y moved by drag
             var x1New = parseFloat(d3.select(this).attr('x1'))+ dx;
             var y1New = parseFloat(d3.select(this).attr('y1'))+ dy;
             var x2New = parseFloat(d3.select(this).attr('x2'))+ dx;
             var y2New = parseFloat(d3.select(this).attr('y2'))+ dy;
             line.attr("x1",x1New)
                 .attr("y1",y1New)
                 .attr("x2",x2New)
                 .attr("y2",y2New);
             }).on('dragend', function(){
           }); 

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工作代码

这在

d3

版本4

及更高版本中不起作用