更改表格列的背景顏色javascript

Question

我想為每個數字設置3和2的倍數的背景色，我該怎么做？ 我不太擅長使用JavaScript

HTML：

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

使用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

這是您檢查的方式（如果可以將其除以2和3）：

if(randNum %2===0 && randNum %3===0){
  // do some
}

Answer 2

如果將td創建的內容放入if else語句中，則可以像下面這樣簡單地進行操作：

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 在這里

Answer 3

這是您可以執行此操作的方法（類似於您的代碼）

var resultTable  = document.createElement('table');
var tr = resultTable.insertRow();

tbl.style.border = '1px solid black';

for (row = 0; row < num; row++){
    var tr = resultTable.insertRow();
    for (col = 0; col < num; col++){
        var td = tr.insertCell();
        var randNum = Math.floor(Math.random() * 100) + 1;
        //for example if you want numbers countable with 2 to be red
        if ((randNum % 2) === 0){
            td.style.backgroundColor = "red";                 
        }                        
        td.appendChild(document.createTextNode(randNum.toString()));
    }
 }
 result.appendChild(resultTable);