Сброс перетаскивания с несколькими элементами

    const circleRadius = 40;
    const variables = ['one', 'two', 'three', 'four'];
    const inZone = [];
    
    // DOM elements
    const svg = d3.select("body").append("svg")
      .attr("width", 960)
      .attr("height", 500)
    
    const dragDockGroup = svg.append('g')
      .attr('id', 'draggables-dock');
    
    const dock = dragDockGroup.selectAll('g')
      .data(variables)
      .enter().append("g")
      .attr("id", (d, i) => `dock-${variables[i]}`);

    dock.append("circle")
      .attr("cx", (d, i) => circleRadius * (2 * i + 1))
      .attr("cy", circleRadius)
      .attr("r", circleRadius)
      .style("stroke", "none")
      .style("fill", "palegoldenrod");

    dock.append("text")
      .attr("x", (d, i) => circleRadius * (2 * i + 1))
      .attr("y", circleRadius)
      .attr("text-anchor", "middle")
      .style("fill", "white")
      .text((d, i) => variables[i]);
    
    const draggablesGroup = svg.append('g')
    	.attr('id', 'draggables');
    
    const draggables = draggablesGroup.selectAll('g')
      .data(variables)
      .enter().append("g")
      .attr("id", (d, i) => variables[i])
      .call(d3.drag()
          .on("start", dragStarted)
          .on("drag", dragged)
          .on("end", dragEnded));

    draggables.append('circle')
      .attr("cx", (d, i) => circleRadius * (2 * i + 1))
      .attr("cy", circleRadius)
      .attr("initial_x", (d, i) => circleRadius * (2 * i + 1))
      .attr("initial_y", circleRadius)
      .attr("r", circleRadius)
      .style("stroke", "orange")
      .style("fill", "yellowgreen");

    draggables.append("text")
       .attr("x", (d, i) => circleRadius * (2 * i + 1))
       .attr("y", circleRadius)
       .attr("text-anchor", "middle")
       .style("fill", "white")
       .text((d, i) => variables[i]);
    
    svg.append('rect')
      .attr("x", 960/2)
      .attr("y", 0)
      .attr("width", 100)
      .attr("height", 500/2)
      .attr("fill-opacity", 0)
      .style("stroke", "#848276")
      .attr("id", "hitZone");
    
    // functions
    function dragStarted() {
      d3.select(this).raise().classed("active", true);
  	}

  	function dragged() {
      d3.select(this).select("text").attr("x", d3.event.x).attr("y", d3.event.y);
      d3.select(this).select("circle").attr("cx", d3.event.x).attr("cy", d3.event.y);
  	}

  function dragEnded() {
    d3.select(this).classed("active", false);
    d3.select(this).lower();
    let hit = d3.select(document.elementFromPoint(d3.event.sourceEvent.clientX, d3.event.sourceEvent.clientY)).attr("id");

    if (hit == "hitZone") {
      inZone.push(this.id);
      if (inZone.length > 1) {
        let resetVar = inZone.shift();
        resetCircle(resetVar);
      }
    }
    
    d3.select(this).raise();
  }

  function resetCircle(resetVar) {
    let current_x = d3.select(`#${resetVar}`)
      .select('circle')
      .attr('cx');

    let current_y = d3.select(`#${resetVar}`)
      .select('circle')
      .attr('cy');

    let initial_x = d3.select(`#${resetVar}`)
      .select('circle')
      .attr('initial_x');

    let initial_y = d3.select(`#${resetVar}`)
      .select('circle')
      .attr('initial_y');

    d3.select(`#${resetVar}`)
      .transition()
        .duration(2000)
        .style('opacity', 0)
      .transition()
        .duration(2000)
        .attr('transform', `translate(${-current_x}, ${-current_y})`)
      .transition()
        .duration(2000)
        .style('opacity', 1);
  }

 body { margin:0;position:fixed;top:0;right:0;bottom:0;left:0; }

 <script src = "https://d3js.org/d3.v5.min.js"></script>