排序表Javascript

Question

当用户单击表头时，我正在对表进行排序，并且我正在使用 vanilla Javascript 来执行此操作。我试图通过单击<th> 表头来捕获列号并将其传递给sortTable(n) 函数。另外，我正在尝试在捕获列数据后启动sortTable(n) 函数。我不确定我的错误在哪里？

document.getElementById('myTable2').addEventListener('click', function() {
  myFunction(event)
}, true);

function myFunction() {
  var col = window.event.target.cellIndex;
  var n = col;
  sortTable(n);
  return n;

}

function sortTable(n) {
  var n = myFunction();
  var table, rows, switching, i, x, y, shouldSwitch, dir, switchcount = 0;
  table = document.getElementById("myTable2");
  switching = true;
  
  dir = "asc";
  while (switching) {
   switching = false;
    rows = table.rows;
    /* Loop through all table rows (except the
    first, which contains table headers): */
    for (i = 1; i < (rows.length - 1); i++) {
      // Start by saying there should be no switching:
      shouldSwitch = false;
      /* Get the two elements you want to compare,
      one from current row and one from the next: */
      x = rows[i].getElementsByTagName("TD")[n];
      y = rows[i + 1].getElementsByTagName("TD")[n];
      /* Check if the two rows should switch place,
      based on the direction, asc or desc: */
      if (dir === "asc") {
        if (x.textContenttextContent.toLowerCase() > y.textContent.toLowerCase()) {
          shouldSwitch = true;
          break;
        }
      } else if (dir === "desc") {
        if (x.textContent.toLowerCase() < y.textContent.toLowerCase()) {
          // If so, mark as a switch and break the loop:
          shouldSwitch = true;
          break;
        }
      }
    }
    if (shouldSwitch) {
      rows[i].parentNode.insertBefore(rows[i + 1], rows[i]);
      switching = true;
      // Each time a switch is done, increase this count by 1:
      switchcount++;
    } else {
       if (switchcount === 0 && dir === "asc") {
        dir = "desc";
        switching = true;
      }
    }
  }
}

Answer 1

呸。您将 eventHandler 称为“myFunction()”的方式存在大量编码问题。在变量作用域方面，您还陷入了一些非常危险的习惯。我重写了那些。从好的方面来说，您的应用程序逻辑是合理的。好工作！ I wrote a pen that works to show it to you in action if the snippet doesn't。但是，请遵循我关于更改变量名称的建议，尤其是在用于赋值时。

document.getElementById('myTable2').addEventListener('click', myFunction, true);

function myFunction(event) {
  // window.alert("In myFunction");
  // console.log(event);
  
  var col = event.target.cellIndex;
  //Following line was redundant;
  //var n = col;
  sortTable(col);
  return col;

}


//PIECE OF ADVICE: If you renamed the variable "n" to "selectedCol", it would be more readable. Or at least "col"
function sortTable(n) {
  // WHY are you redeclaring the argument?
  // And why are you assigning myFunction, which called this function, as the object which you are assigning to n?
//   var n = myFunction();

  // OLD VERSION: All declared and set to 0, then later reassigned: Confusing and can get you into problems with variable scope, and unused declarations. 
  // var table, rows, switching, i, x, y, shouldSwitch, dir, switchcount = 0;
  var switchcount = 0;
  
  var table = document.getElementById("myTable2");
  var switching = true;
  var dir = "asc";

  while (switching) {
   switching = false;
   var rows = table.rows;
    var shouldSwitch;

    /* Loop through all table rows (except the
    first, which contains table headers): */
    for (var i = 1; i < (rows.length - 1); i++) {
      // Start by saying there should be no switching:
      shouldSwitch = false;
      /* Get the two elements you want to compare,
      one from current row and one from the next: */
      var x = rows[i].getElementsByTagName("TD")[n];
      var y = rows[i + 1].getElementsByTagName("TD")[n];
      /* Check if the two rows should switch place,
      based on the direction, asc or desc: */
      if (dir === "asc") {
        if (x.textContent.toLowerCase() > y.textContent.toLowerCase()) {
          shouldSwitch = true;
          break;
        }
      } else if (dir === "desc") {
        if (x.textContent.toLowerCase() < y.textContent.toLowerCase()) {
          // If so, mark as a switch and break the loop:
          shouldSwitch = true;
          break;
        }
      }
    }
    if (shouldSwitch) {
      rows[i].parentNode.insertBefore(rows[i + 1], rows[i]);
      switching = true;
      // Each time a switch is done, increase this count by 1:
      switchcount++;
    } else {
       if (switchcount === 0 && dir === "asc") {
        dir = "desc";
        switching = true;
      }
    }
  }
}

table, th, td {
    border: 1px solid black;
    border-collapse: collapse;
}
th, td {
    padding: 5px;
}
th {
    text-align: left;
}

<table id = "myTable2" style="width:100%">
  <tr>
    <th>Firstname</th>
    <th>Lastname</th> 
    <th>Age</th>
  </tr>
  <tr>
    <td>Jill</td>
    <td>Smith</td>
    <td>50</td>
  </tr>
  <tr>
    <td>Eve</td>
    <td>Jackson</td>
    <td>94</td>
  </tr>
  <tr>
    <td>John</td>
    <td>Doe</td>
    <td>80</td>
  </tr>
</table>