javascript - 需要在更改下拉列表中突出显示区域坐标

Question

请看下面我的代码。我需要突出显示在下拉选项中选择的那些区域。

<select name="hightlight" multiple>
<option value="20">20</option>
<option value="21">21</option>
<option value="22">22</option>
<option value="23">23</option>
<option value="24">24</option>
<option value="25">25</option>
<option value="26">26</option>
<option value="27">27</option>
<option value="28">28</option>
<option value="29">29</option>
<option value="30">30</option>
</select>



<div class="inner-profile-map1">
                                <img src="images/plot_map.png" alt="" usemap="#Map">                        
                            </div>
                            <map name="Map">
                                <area class="area1 thumbLink area_21" shape="poly" coords="115,315,64,270,103,229,151,273">
                                <area class="area2 thumbLink area_22" shape="poly" coords="155,269,106,225,142,185,191,230">
                                <area class="area3 thumbLink area_21" shape="poly" coords="147,182,182,144,231,187,194,227">
                                <area class="area4 thumbLink area_23" shape="poly" coords="185,140,241,77,267,137,274,145,236,183" >
                                <area class="area5 thumbLink area_20" shape="poly" coords="278,143,270,134,246,75,253,66,315,62,319,131,302,131">
                                <area class="area6 thumbLink area_20" shape="poly" coords="325,129,320,63,368,60,370,126">
                                <area class="area7 thumbLink area_20" shape="poly" coords="375,127,374,60,445,56,422,131,406,127">
                                <area class="area8 thumbLink area_22" shape="poly" coords="446,149,497,95,537,131,487,186">
                                <area class="area9 thumbLink area_23" shape="poly" coords="490,189,540,134,579,168,527,225">
                                <area class="area10 thumbLink area_23" shape="poly" coords="531,227,582,172,620,207,569,263">
                                <area class="area11 thumbLink area_28" shape="poly" coords="573,266,624,210,663,246,611,300">
                                <area class="area12 thumbLink area_29" shape="poly" coords="616,304,666,249,704,284,653,338">
                                <area class="area13 thumbLink area_29" shape="poly" coords="657,343,709,288,747,323,697,378">
                                <area class="area14 thumbLink area_27" shape="poly" coords="702,382,752,327,790,361,740,417">
                                <area class="area15 thumbLink area_27" shape="poly" coords="743,420,794,365,831,400,782,456">
                                <area class="area16 thumbLink area_23" shape="poly" coords="787,460,838,404,876,442,829,498">
                                <area class="area17 thumbLink area_23" shape="poly" coords="766,480,807,518,768,564,727,525">
                                <area class="area18 thumbLink area_20" shape="poly" coords="724,441,763,476,723,520,684,486">
                                <area class="area19 thumbLink area_20" shape="poly" coords="680,402,719,438,680,481,642,445">
                                <area class="area20 thumbLink area_20" shape="poly" coords="638,363,677,397,637,441,600,406">
                                <area class="area21 thumbLink area_25" shape="poly" coords="594,323,635,360,595,403,557,367">
                                <area class="area22 thumbLink area_25" shape="poly" coords="219,256,256,217,299,255,263,296">
                                <area class="area23 thumbLink area_24" shape="poly" coords="183,299,217,260,258,300,224,335">
                                <area class="area24 thumbLink area_26" shape="poly" coords="143,340,180,302,221,341,186,379">
                            </map>
                        </div>

当我更改下拉列表时，我需要突出显示与区域类别匹配的区域。我曾尝试为 CSS 和 JQuery 做，但两者都不起作用。请让我知道我是怎么做到的。

Answer 1

window.addEventListener('load', function() {
  /* GET FIRST IMAGE TAG AND ADD SOME CSS TO IT */
  var img = document.querySelector('img');
  img.style.position = 'absolute';
  img.style.display = 'block';
  img.style.border = '1px solid red';

  /* CANVAS ELEMENT CREATION, AND SOME CSS */
  var canvas = document.createElement('canvas');
  canvas.style.border = '1px solid blue';
  canvas.style.position = 'absolute';
  canvas.style.pointerEvents = 'none';
  canvas.width = img.clientWidth;
  canvas.height = img.clientHeight;

  /* INSERTES 'canvas' TO '.inner-profile-map1' */
  var wrap = document.querySelector('.inner-profile-map1');
  wrap.appendChild(canvas);

  /* GETS THE CANVAS CONTEXT */
  var ctx = canvas.getContext('2d');

  var select = document.body.querySelector('select');

  /* ADDS BACKGROUND COLOR TO EACH OPTION */
  select.querySelectorAll('option').forEach(function(option) {
    option.style.backgroundColor = option.getAttribute('data-color');
  });

  /* LISTENS FOR SELECT CHANGE */
  select.addEventListener('change', function(event) {
    /* CLEARS WHOLE CANVAS */
    ctx.clearRect(0, 0, canvas.width, canvas.height);

    /* GET ALL SELECTED OPTIONS */
    var options = this.querySelectorAll('option:checked');

    /* FOR EACH OPTION GET COORDINATES, DATA-COLOR AND DRAW COORDINATES */
    options.forEach(function(option) {
      /* FINDS ALL AREAS ASSOCIATED WITH OPTION */
      var areas = document.body.querySelectorAll(`.area_${option.value}`);
      var color = option.getAttribute('data-color') || 'rgba(255, 255, 255, 0.5)';

      /* DRAW EACH AREA COORDINATES */
      areas.forEach(function(area) {
        var coords = area.getAttribute('coords').split(',');

        /* DRAW THE AREA COORDINATES */
        ctx.beginPath();
        ctx.moveTo(coords[0], coords[1]);
        for (var n=2; n<coords.length; n+=2) {
          ctx.lineTo(coords[n], coords[n+1]);
        }
        ctx.lineTo(coords[0], coords[1]);
        ctx.fillStyle = color;
        ctx.stroke();
        ctx.fill();
      });
    });
  });
});

<select name="hightlight" multiple>
  <option value="20" data-color="rgba(255, 0, 0, 0.5)">20</option>
  <option value="21" data-color="rgba(255, 0, 255, 0.5)">21</option>
  <option value="22" data-color="rgba(0, 255, 0, 0.5)">22</option>
  <option value="23">23</option>
  <option value="24">24</option>
  <option value="25">25</option>
  <option value="26">26</option>
  <option value="27">27</option>
  <option value="28">28</option>
  <option value="29">29</option>
  <option value="30">30</option>
</select>



<div class="inner-profile-map1">
  <img src="/image/J3uwz.jpg" alt="" usemap="#Map">                        
</div>

<map name="Map">
  <area class="area1 thumbLink area_21" shape="poly" coords="115,315,64,270,103,229,151,273">
  <area class="area2 thumbLink area_22" shape="poly" coords="155,269,106,225,142,185,191,230">
  <area class="area3 thumbLink area_21" shape="poly" coords="147,182,182,144,231,187,194,227">
  <area class="area4 thumbLink area_23" shape="poly" coords="185,140,241,77,267,137,274,145,236,183" >
  <area class="area5 thumbLink area_20" shape="poly" coords="278,143,270,134,246,75,253,66,315,62,319,131,302,131">
  <area class="area6 thumbLink area_20" shape="poly" coords="325,129,320,63,368,60,370,126">
  <area class="area7 thumbLink area_20" shape="poly" coords="375,127,374,60,445,56,422,131,406,127">
  <area class="area8 thumbLink area_22" shape="poly" coords="446,149,497,95,537,131,487,186">
  <area class="area9 thumbLink area_23" shape="poly" coords="490,189,540,134,579,168,527,225">
  <area class="area10 thumbLink area_23" shape="poly" coords="531,227,582,172,620,207,569,263">
  <area class="area11 thumbLink area_28" shape="poly" coords="573,266,624,210,663,246,611,300">
  <area class="area12 thumbLink area_29" shape="poly" coords="616,304,666,249,704,284,653,338">
  <area class="area13 thumbLink area_29" shape="poly" coords="657,343,709,288,747,323,697,378">
  <area class="area14 thumbLink area_27" shape="poly" coords="702,382,752,327,790,361,740,417">
  <area class="area15 thumbLink area_27" shape="poly" coords="743,420,794,365,831,400,782,456">
  <area class="area16 thumbLink area_23" shape="poly" coords="787,460,838,404,876,442,829,498">
  <area class="area17 thumbLink area_23" shape="poly" coords="766,480,807,518,768,564,727,525">
  <area class="area18 thumbLink area_20" shape="poly" coords="724,441,763,476,723,520,684,486">
  <area class="area19 thumbLink area_20" shape="poly" coords="680,402,719,438,680,481,642,445">
  <area class="area20 thumbLink area_20" shape="poly" coords="638,363,677,397,637,441,600,406">
  <area class="area21 thumbLink area_25" shape="poly" coords="594,323,635,360,595,403,557,367">
  <area class="area22 thumbLink area_25" shape="poly" coords="219,256,256,217,299,255,263,296">
  <area class="area23 thumbLink area_24" shape="poly" coords="183,299,217,260,258,300,224,335">
  <area class="area24 thumbLink area_26" shape="poly" coords="143,340,180,302,221,341,186,379">
</map>
  </div>