Question

我正在尝试编写一个脚本，该脚本采用表的第一列中的方法（字符串形式），并在每一行的第三列中显示该方法的输出。例如html表的第1行第1列包含.getFullYear（），因此在第3列中，我现在要运行（我的Date对象）.getFullYear（）。在下一行中，我将立即运行now.getMonth（）等等。

当我运行eval（“ now。” + method）时，它没有问题，但是我试图避免使用eval（）。当我现在运行[方法]时，输出返回未定义。为什么eval（）可以工作，但是现在[方法]返回不同的东西？

```JavaScript`

const now = new Date();
//gets the full table data
const methodTable = document.querySelector("#methods-table");

function tableTimeData(table) {
    const tableLength = table.rows.length;
    for (let i = 1; i < tableLength; i++) { //iterate through each table row, skipping the header
        let row = table.rows[i];
        let method = row.cells[0].innerText;
        row.cells[2].innerText = eval("now." + method);
        //OR
        method = method.substr(1);
        row.cells[2].innerText = now[method];
    }
}

tableTimeData(methodTable);

HTML

   <table class="table" id="methods-table">
                <tr>
                    <th>Method Name</th>
                    <th>Method Description</th>
                    <th>Method Output</th>
                </tr>
                <tr>
                    <td class="text-info font-weight-bold">.getFullYear()</td>
                    <td>Returns the full 4 digit year.</td>
                    <td></td>
                </tr>
                <tr>
                    <td class="text-info font-weight-bold">.getMonth()</td>
                    <td>Returns the month as an integer (0-11).</td>
                    <td></td>
                </tr>
                <tr>
                    <td class="text-info font-weight-bold">.getDay()</td>
                    <td>Returns the day of the week as an integer (0-6).</td>
                    <td></td>
                </tr>
                <tr>
                    <td class="text-info font-weight-bold">.getHours()</td>
                    <td>Returns the hour as of creation.</td>
                    <td></td>
                </tr>
                <tr>
                    <td class="text-info font-weight-bold">.getMinutes()</td>
                    <td>Returns minute as of creation</td>
                    <td></td>
                </tr>
                <tr>
                    <td class="text-info font-weight-bold">.getSeconds()</td>
                    <td>Returns second as of creation</td>
                    <td></td>
                </tr>
                <tr>
                    <td class="text-info font-weight-bold">.getTime()</td>
                    <td>Returns the number of miliseconds passed since Jan. 1 1970. Used as a baseline to compare 2 dates.</td>
                    <td></td>
                </tr>
                <tr>
                    <td class="text-info font-weight-bold">.toDateString()</td>
                    <td>Returns a shortened date with day, month, date and year with day and month as names rather than integers.</td>
                    <td></td>
                </tr>
                <tr>
                    <td class="text-info font-weight-bold">.toTimeString()</td>
                    <td>Returns a shortened time of day with hour, minute second and time zone (always Greenwhich Mean Time as a standard).</td>
                    <td></td>
                </tr>
                <tr>
                    <td class="text-info font-weight-bold">.toLocaleString()</td>
                    <td>Returns a shortened time of day with hour, minute second and time zone (as your local time zone).</td>
                    <td></td>
                </tr>
            </table>

我希望eval（“ now。” + method）的结果与now [method]相同。

Answer 1

如果method是.getFullYear()，则

method = method.slice(1, -2);
row.cells[2].innerText = now[method]();

应该工作。您忘记从()中删除method

为什么object.eval（）有效，方括号返回undefined？

1 个答案: