D3 Examples - Stopwatch

Stopwatch

A stopwatch app constructed using d3-component.

The following components are defined and used to construct the app:

app
The top-level app component. This serves as a "container component" that holds the state of the app, and exposes "actions" to children (similar pattern to Redux. This component manages an instance of d3-timer that keeps track of passing time.

buttonPanel
The panel that contains the two buttons. This shows a simple composition pattern in which props are passed through to child components.

resetButton
The button that says "Reset" and invokes the reset action when clicked.

startStopButton
The button that either starts or stops (pauses) the stopwatch when clicked, depending on whether the stopwatch is running or not.

button
A generic Button component, used by both resetButton and startStopButton.

timeDisplay
A display of the current time.

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<!DOCTYPE html>
<head>
  <meta charset="utf-8">
  <script src="https://unpkg.com/d3@4"></script>
  <script src="https://unpkg.com/d3-component@1"></script>
  <style>
    body {
      text-align: center;
      margin-top: 75px;
    }
    .time-display {
      color: #3d3d3d;
      font-size: 10em;
      font-family: mono;
      cursor: default;
    }
    button {
      background-color: #7c7c7c;
      border: solid 3px #7c7c7c;
      border-radius: 11px;
      color: white;
      padding: 20px 60px;
      margin: 20px;
      font-size: 58px;
      cursor: pointer;
    }
    button:hover {
      border: solid 3px black;
    }
    button:focus {
      outline: none;
    }
  </style>
</head>
<body>
  <script>
    
    // This function formats the stopwatch time.
    var stopwatchFormat = (function (){
      var twoDigits = d3.format("02.0f");
      return function (milliseconds){
        var centiseconds = Math.floor(milliseconds / 10),
            centisecond = centiseconds % 100,
            seconds = Math.floor(centiseconds /100),
            second = seconds % 60,
            minutes = Math.floor(seconds / 60),
            minute = minutes % 60,
            hours = Math.floor(minutes / 60);
        return [
          hours >= 1 ? hours + ":" : "",
          minutes >= 1 ? (
            (hours >= 1 ? twoDigits(minute) : minute) + ":"
          ) : "",
          (minutes >= 1 ? twoDigits(second) : second),
          hours < 1 ? ":" + twoDigits(centisecond) : "",
        ].join("").replace(/0/g, "O"); // Don't show the dot in the zeros.
      }
    }());
    
    // A component that renders the formatted stopwatch time.
    var timeDisplay = d3.component("div", "time-display")
      .update(function (d){
        d3.select(this).text(stopwatchFormat(d.totalTime)); 
      });
    
    // A generic Button component.
    var button = d3.component("button")
      .update(function (d){
        d3.select(this)
            .text(d.text)
            .on("click", d.onClick);
      });
    
    // The button that either starts or stops (pauses) the stopwatch,
    //depending on whether the stopwatch is running or not. 
    var startStopButton = d3.component("span")
      .update(function (d){
        var stopped = d.mode === "stopped";
        d3.select(this).call(button, {
          text: stopped ? "Start" : "Stop",
          onClick: stopped ? d.actions.start : d.actions.stop
        });
      });
    
    // The reset button that stops and resets the stopwatch.
    var resetButton = d3.component("span")
      .update(function (d){
        d3.select(this).call(button, {
          text: "Reset",
          onClick: d.actions.reset
        });
      });
    
    // The panel that contains the two buttons.
    var buttonPanel = d3.component("div")
      .update(function (d){
        d3.select(this)
          .call(startStopButton, d)
          .call(resetButton, d);
      });
    
    // The top-level app component.
    var app = d3.component("div")
      .update(function (d){
        d3.select(this)
            .call(timeDisplay, d)
            .call(buttonPanel, d);
      });
    
    // DIY Redux - would not recommend.
    // TODO update this example to use Redux proper.
    function main(){
      var state = {};
      
      function setState(newState){
        if(typeof newState === "function"){
          newState = newState(state);
        }
        Object.assign(state, newState);
        d3.select("body").call(app, state);
      }
      
      var actions = {
        start: function (){
          setState(function (state){
            return {
              mode: "started",
              timer: d3.timer(function (elapsed){
                setState({
                  totalTime: state.stopTime + elapsed
                });
              })
            };
          });
        },
        stop: function (){
          setState(function (state){
            state.timer.stop();
            return {
              mode: "stopped",
              stopTime: state.totalTime
            };
          });
        },
        reset: function (){
          setState(function (state){
            state.timer && state.timer.stop();
            return {
              mode: "stopped",
              totalTime: 0,
              stopTime: 0
​
              // Test cases for formatter:
              //stopTime: 58000 // 58 seconds
              //stopTime: 60000 * 59 + 58000 // 59 minutes 58 seconds
            };
          });
        }
      };
      setState({
        actions: actions
      });
      
      actions.reset();
    }
    main();
  </script>
</body>
    