jquery - 更新 D3 图表导致重复图表

Question

我在尝试在单击按钮后将 JSON 数据更新为 D3 直方图时遇到了麻烦。

虽然我解决了单击按钮更新问题，但 D3 javascript 现在每次单击按钮都会附加一个图表，从而导致出现重复的图表，而不是简单地更新数据。

据我了解，每次触发点击事件时都会在 D3 代码中调用 append()，但如何解决此问题，以便每次点击时只有一个图表包含更新的数据？

console.log('chart.js loaded');

$(document).ready(function() {

  var vimeoVideoId = $('p#vimeoVideoId').text();
  var api = 'http://localhost:3001/videos/' + vimeoVideoId + '/json';

  function initData() {
    $('#all-notes').click(function() {
      getData();
    });
  }

  function getData() {
    $.getJSON(api, draw);
  }

  function draw(json) {

    data = json;
    var duration = data.duration;

    var timeToSec = function(data) {
      notes = [];
      // convert min:sec to seconds
      for(i=0; i < data.notes.length; i++) {
        var min_sec = data.notes[i].timecode;
        var tt = min_sec.split(':');
        var seconds = tt[0]*60+tt[1]*1;
        notes.push(seconds);
      }
      return notes;
    };

    noteTimes = timeToSec(data);
    console.log(noteTimes);

    // Formatters for counts and times (converting numbers to Dates).
    var formatCount = d3.format(",.0f"),
        formatTime = d3.time.format("%H:%M"),
        formatMinutes = function(d) { return formatTime(new Date(2012, 0, 1, 0, d)); };

    var margin = {top: 10, right: 20, bottom: 30, left: 20},
        width = 550;
        height = 285;

    var x = d3.scale.linear()
        .domain([0, duration])
        // .domain([0, d3.max(noteTimes)])
        .range([0, width]);

    // Generate a histogram using twenty uniformly-spaced bins.
    var data = d3.layout.histogram()
        .bins(x.ticks(50))
        (noteTimes);

    var y = d3.scale.linear()
        .domain([0, d3.max(data, function(d) { return d.y; })])
        .range([height, 0]);

    var xAxis = d3.svg.axis()
        .scale(x)
        .orient("bottom")
        .tickFormat(formatMinutes);

    var svg = d3.select("#chartSet").append("svg")
        .attr("width", width + margin.left + margin.right)
        .attr("height", height + margin.top + margin.bottom)
      .append("g")
        .attr("transform", "translate(" + margin.left + "," + margin.top + ")");

    var bar = svg.selectAll(".bar")
        .data(data)
      .enter().append("g")
        .attr("class", "bar")
        .attr("transform", function(d) { return "translate(" + x(d.x) + "," + y(d.y) + ")"; });

    bar.append("rect")
        .attr("x", 1)
        .attr("width", x(data[0].dx) - 1)
        .attr("height", function(d) { return height - y(d.y); });

    bar.append("text")
        .attr("dy", ".75em")
        .attr("y", 6)
        .attr("x", x(data[0].dx) / 2)
        .attr("text-anchor", "middle")
        .text(function(d) { return formatCount(d.y); });

    svg.append("g")
        .attr("class", "x axis")
        .attr("transform", "translate(0," + height + ")")
        .call(xAxis);
  }

  initData();

});

Answer 1

要处理创建和更新，您必须重新组织 draw 函数的编写方式。

function draw(json) {

   // Initialization (few wasted CPU cycles)
   // ...

   // Update hook
   var svg = d3.select("#chartSet").data([data]);

   // Enter hook
   var svgEnter = svg.enter();

   // Enter cycle
   svgEnter.append("svg")
      .append("g")
      .attr("transform", "translate(" + margin.left + "," + margin.top + ")");

    // Update cycle
    svg
        .attr("width", width + margin.left + margin.right)
        .attr("height", height + margin.top + margin.bottom);

    // Exit cycle (not really needed here)
    svg.exit().remove();

    // Update hook
    var bar = svg.selectAll(".bar")
        .data(data)

    // Enter hook
    var barEnter = bar.enter();

    // Enter cycle
    var barG_Enter = barEnter
                        .append("g")
                        .attr("class", "bar")
    barG_Enter
        .append("rect")
        .attr("x", 1);

    barG_Enter
        .append("text")
        .attr("dy", ".75em")
        .attr("y", 6)
        .attr("text-anchor", "middle");

    // Update cycle
    bar.attr("transform", function(d) { 
        return "translate(" + x(d.x) + "," + y(d.y) + ")"; });

    bar.select("rect")
        .attr("width", x(data[0].dx) - 1)
        .attr("height", function(d) { return height - y(d.y); });

    bar.select("text")
        .attr("x", x(data[0].dx) / 2)
        .text(function(d) { return formatCount(d.y); });

    // Exit cycle
    bar.exit().remove();

    // Enter cycle
    svgEnter.append("g")
        .attr("class", "x axis")
        .attr("transform", "translate(0," + height + ")")
        .call(xAxis);

    // Update cycle
    svg.select('g.x.axis')
        .call(xAxis);
}

这个classical enter-update-exit模式在 this article on making reusable graphs 中得到改进。这个答案很大程度上借鉴了这种模式。

通过使用闭包的稍微更好的实现，您将能够节省每次初始化时浪费的几个 CPU 周期。