javascript - 更改表格列javascript的背景颜色

Question

我想为每个 3 和 2 的倍数的数字设置背景颜色，我该怎么做？我不太擅长这个 javascript 的东西

HTML:

<div id="mainDiv">
    <input type="text" id="myNo" />
    <input type="button" id="gridSize" value="Show It" />
</div>

Javascript:

var button = document.getElementById('gridSize');
 button.onclick = function(e){
    result  = document.getElementById('result');
    num = parseInt(document.getElementById('myNo').value);
    alert(num);
    if ( isNaN(num) ){
        alert("No Numeric Value!");
    }
    else{
        result.innerHTML = num;
    }
    var str = "<table border='2'>";
    for (row = 0; row < num; row++){
    str += "<tr>";
        for (col = 0; col < num; col++){
            str += "<td>";
            var randNum = Math.floor(Math.random() * 100) + 1;
            if (randNum % 2){
                console.log(randNum + "Red");
            }
            str += randNum;
            str += "</td>";
        }
        str += "</tr>";
     }
     str = str + "</table>";
     result.innerHTML = str;
}

Answer 1

如果你将你的 td 创作放入一个 if else 语句中，你可以像这样非常简单地做到这一点:

HTML

<div id="mainDiv">
  <input type="text" id="myNo" />
  <input type="button" id="gridSize" value="Show It" />
</div>

<div id="result"></div>

CSS

.two {
  background: red;
}

.three {
  background: blue;
}

JS

var button = document.getElementById('gridSize');
button.onclick = function(e) {
  result = document.getElementById('result');
  num = parseInt(document.getElementById('myNo').value);
  alert(num);
  if (isNaN(num)) {
    alert("No Numeric Value!");
  } else {
    result.innerHTML = num;
  }
  var str = "<table border='2'>";
  for (row = 0; row < num; row++) {
    str += "<tr>";
    for (col = 0; col < num; col++) {
      var randNum = Math.floor(Math.random() * 100) + 1;
      if (randNum % 2 === 0) {
        str += '<td class="two">';
      } else if (randNum % 3 === 0) {
        str += '<td class="three">';
      } else {
        str += "<td>";
      }
      str += randNum + "</td>";
    }
    str += "</tr>";
  }
  str = str + "</table>";
  result.innerHTML = str;
}

jsfiddle here