How to delete all the shape after draw

Question

Refer from this source google map drawing tools, how to deleted all the drawing shape by one click button?

code snippet:

var drawingManager;
      var selectedShape;
      var colors = ['#1E90FF', '#FF1493', '#32CD32', '#FF8C00', '#4B0082'];
      var selectedColor;
      var colorButtons = {};

      function clearSelection() {
        if (selectedShape) {
          selectedShape.setEditable(false);
          selectedShape = null;
        }
      }

      function setSelection(shape) {
        clearSelection();
        selectedShape = shape;
        shape.setEditable(true);
        selectColor(shape.get('fillColor') || shape.get('strokeColor'));
      }

      function deleteSelectedShape() {
        if (selectedShape) {
          selectedShape.setMap(null);
        }
      }

      function selectColor(color) {
        selectedColor = color;
        for (var i = 0; i < colors.length; ++i) {
          var currColor = colors[i];
          colorButtons[currColor].style.border = currColor == color ? '2px solid #789' : '2px solid #fff';
        }

        // Retrieves the current options from the drawing manager and replaces the
        // stroke or fill color as appropriate.
        var polylineOptions = drawingManager.get('polylineOptions');
        polylineOptions.strokeColor = color;
        drawingManager.set('polylineOptions', polylineOptions);

        var rectangleOptions = drawingManager.get('rectangleOptions');
        rectangleOptions.fillColor = color;
        drawingManager.set('rectangleOptions', rectangleOptions);

        var circleOptions = drawingManager.get('circleOptions');
        circleOptions.fillColor = color;
        drawingManager.set('circleOptions', circleOptions);

        var polygonOptions = drawingManager.get('polygonOptions');
        polygonOptions.fillColor = color;
        drawingManager.set('polygonOptions', polygonOptions);
      }

      function setSelectedShapeColor(color) {
        if (selectedShape) {
          if (selectedShape.type == google.maps.drawing.OverlayType.POLYLINE) {
            selectedShape.set('strokeColor', color);
          } else {
            selectedShape.set('fillColor', color);
          }
        }
      }

      function makeColorButton(color) {
        var button = document.createElement('span');
        button.className = 'color-button';
        button.style.backgroundColor = color;
        google.maps.event.addDomListener(button, 'click', function() {
          selectColor(color);
          setSelectedShapeColor(color);
        });

        return button;
      }

       function buildColorPalette() {
         var colorPalette = document.getElementById('color-palette');
         for (var i = 0; i < colors.length; ++i) {
           var currColor = colors[i];
           var colorButton = makeColorButton(currColor);
           colorPalette.appendChild(colorButton);
           colorButtons[currColor] = colorButton;
         }
         selectColor(colors[0]);
       }

      function initialize() {
        var map = new google.maps.Map(document.getElementById('map'), {
          zoom: 10,
          center: new google.maps.LatLng(22.344, 114.048),
          mapTypeId: google.maps.MapTypeId.ROADMAP,
          disableDefaultUI: true,
          zoomControl: true
        });

        var polyOptions = {
          strokeWeight: 0,
          fillOpacity: 0.45,
          editable: true
        };
        // Creates a drawing manager attached to the map that allows the user to draw
        // markers, lines, and shapes.
        drawingManager = new google.maps.drawing.DrawingManager({
          drawingMode: google.maps.drawing.OverlayType.POLYGON,
          markerOptions: {
            draggable: true
          },
          polylineOptions: {
            editable: true
          },
          rectangleOptions: polyOptions,
          circleOptions: polyOptions,
          polygonOptions: polyOptions,
          map: map
        });

        google.maps.event.addListener(drawingManager, 'overlaycomplete', function(e) {
            if (e.type != google.maps.drawing.OverlayType.MARKER) {
            // Switch back to non-drawing mode after drawing a shape.
            drawingManager.setDrawingMode(null);

            // Add an event listener that selects the newly-drawn shape when the user
            // mouses down on it.
            var newShape = e.overlay;
            newShape.type = e.type;
            google.maps.event.addListener(newShape, 'click', function() {
              setSelection(newShape);
            });
            setSelection(newShape);
          }
        });

        // Clear the current selection when the drawing mode is changed, or when the
        // map is clicked.
        google.maps.event.addListener(drawingManager, 'drawingmode_changed', clearSelection);
        google.maps.event.addListener(map, 'click', clearSelection);
        google.maps.event.addDomListener(document.getElementById('delete-button'), 'click', deleteSelectedShape);

        buildColorPalette();
      }
      google.maps.event.addDomListener(window, 'load', initialize);

#map, html, body {
        padding: 0;
        margin: 0;
        height: 100%;
      }

      #panel {
        width: 200px;
        font-family: Arial, sans-serif;
        font-size: 13px;
        float: right;
        margin: 10px;
      }

      #color-palette {
        clear: both;
      }

      .color-button {
        width: 14px;
        height: 14px;
        font-size: 0;
        margin: 2px;
        float: left;
        cursor: pointer;
      }

      #delete-button {
        margin-top: 5px;
      }

<script src="http://maps.google.com/maps/api/js?libraries=drawing"></script>
    <div id="panel">
      <div id="color-palette"></div>
      <div>
        <button id="delete-button">Delete Selected Shape</button>
      </div>
    </div>
    <div id="map"></div>

Answer 1

If you want to delete (or do anything with) all the objects on the map, you need to keep references to them that you can use.

1. When a shape is created, push it into an array (needs to be global to be used in a button click handler).
2. When the "delete all" button is clicked, iterate through that array, calling .setMap(null) on each of the objects.

Example

Push the overlay onto an array (all_overlays):

google.maps.event.addListener(drawingManager, 'overlaycomplete', function(e) {
    all_overlays.push(e);
    if (e.type != google.maps.drawing.OverlayType.MARKER) {
    // Switch back to non-drawing mode after drawing a shape.
    drawingManager.setDrawingMode(null);
    // Add an event listener that selects the newly-drawn shape when the user
    // mouses down on it.
    var newShape = e.overlay;
    newShape.type = e.type;
    google.maps.event.addListener(newShape, 'click', function() {
      setSelection(newShape);
    });
    setSelection(newShape);
  }
});

Delete all shapes:

function deleteAllShape() {
  for (var i=0; i < all_overlays.length; i++)
  {
    all_overlays[i].overlay.setMap(null);
  }
  all_overlays = [];
}

Code snippet:

var drawingManager;
var all_overlays = [];
var selectedShape;
var colors = ['#1E90FF', '#FF1493', '#32CD32', '#FF8C00', '#4B0082'];
var selectedColor;
var colorButtons = {};

function clearSelection() {
  if (selectedShape) {
    selectedShape.setEditable(false);
    selectedShape = null;
  }
}

function setSelection(shape) {
  clearSelection();
  selectedShape = shape;
  shape.setEditable(true);
  selectColor(shape.get('fillColor') || shape.get('strokeColor'));
}

function deleteSelectedShape() {
  if (selectedShape) {
    selectedShape.setMap(null);
  }
}

function deleteAllShape() {
  for (var i = 0; i < all_overlays.length; i++) {
    all_overlays[i].overlay.setMap(null);
  }
  all_overlays = [];
}

function selectColor(color) {
  selectedColor = color;
  for (var i = 0; i < colors.length; ++i) {
    var currColor = colors[i];
    colorButtons[currColor].style.border = currColor == color ? '2px solid #789' : '2px solid #fff';
  }

  // Retrieves the current options from the drawing manager and replaces the
  // stroke or fill color as appropriate.
  var polylineOptions = drawingManager.get('polylineOptions');
  polylineOptions.strokeColor = color;
  drawingManager.set('polylineOptions', polylineOptions);

  var rectangleOptions = drawingManager.get('rectangleOptions');
  rectangleOptions.fillColor = color;
  drawingManager.set('rectangleOptions', rectangleOptions);

  var circleOptions = drawingManager.get('circleOptions');
  circleOptions.fillColor = color;
  drawingManager.set('circleOptions', circleOptions);

  var polygonOptions = drawingManager.get('polygonOptions');
  polygonOptions.fillColor = color;
  drawingManager.set('polygonOptions', polygonOptions);
}

function setSelectedShapeColor(color) {
  if (selectedShape) {
    if (selectedShape.type == google.maps.drawing.OverlayType.POLYLINE) {
      selectedShape.set('strokeColor', color);
    } else {
      selectedShape.set('fillColor', color);
    }
  }
}

function makeColorButton(color) {
  var button = document.createElement('span');
  button.className = 'color-button';
  button.style.backgroundColor = color;
  google.maps.event.addDomListener(button, 'click', function() {
    selectColor(color);
    setSelectedShapeColor(color);
  });

  return button;
}

function buildColorPalette() {
  var colorPalette = document.getElementById('color-palette');
  for (var i = 0; i < colors.length; ++i) {
    var currColor = colors[i];
    var colorButton = makeColorButton(currColor);
    colorPalette.appendChild(colorButton);
    colorButtons[currColor] = colorButton;
  }
  selectColor(colors[0]);
}

function initialize() {
  var map = new google.maps.Map(document.getElementById('map'), {
    zoom: 10,
    center: new google.maps.LatLng(22.344, 114.048),
    mapTypeId: google.maps.MapTypeId.ROADMAP,
    disableDefaultUI: true,
    zoomControl: true
  });

  var polyOptions = {
    strokeWeight: 0,
    fillOpacity: 0.45,
    editable: true
  };
  // Creates a drawing manager attached to the map that allows the user to draw
  // markers, lines, and shapes.
  drawingManager = new google.maps.drawing.DrawingManager({
    drawingMode: google.maps.drawing.OverlayType.POLYGON,
    markerOptions: {
      draggable: true
    },
    polylineOptions: {
      editable: true
    },
    rectangleOptions: polyOptions,
    circleOptions: polyOptions,
    polygonOptions: polyOptions,
    map: map
  });

  google.maps.event.addListener(drawingManager, 'overlaycomplete', function(e) {
    all_overlays.push(e);
    if (e.type != google.maps.drawing.OverlayType.MARKER) {
      // Switch back to non-drawing mode after drawing a shape.
      drawingManager.setDrawingMode(null);

      // Add an event listener that selects the newly-drawn shape when the user
      // mouses down on it.
      var newShape = e.overlay;
      newShape.type = e.type;
      google.maps.event.addListener(newShape, 'click', function() {
        setSelection(newShape);
      });
      setSelection(newShape);
    }
  });

  // Clear the current selection when the drawing mode is changed, or when the
  // map is clicked.
  google.maps.event.addListener(drawingManager, 'drawingmode_changed', clearSelection);
  google.maps.event.addListener(map, 'click', clearSelection);
  google.maps.event.addDomListener(document.getElementById('delete-button'), 'click', deleteSelectedShape);
  google.maps.event.addDomListener(document.getElementById('delete-all-button'), 'click', deleteAllShape);

  buildColorPalette();
}
google.maps.event.addDomListener(window, 'load', initialize);

#map,
html,
body {
  padding: 0;
  margin: 0;
  height: 100%;
}
#panel {
  width: 200px;
  font-family: Arial, sans-serif;
  font-size: 13px;
  float: right;
  margin: 10px;
}
#color-palette {
  clear: both;
}
.color-button {
  width: 14px;
  height: 14px;
  font-size: 0;
  margin: 2px;
  float: left;
  cursor: pointer;
}
#delete-button {
  margin-top: 5px;
}

<script src="http://maps.google.com/maps/api/js?libraries=drawing"></script>
<div id="panel">
  <div id="color-palette"></div>
  <div>
    <button id="delete-button">Delete Selected Shape</button>
    <button id="delete-all-button">Delete All Shapes</button>
  </div>
</div>
<div id="map"></div>