javascript - 注释代码会改变先前代码的行为

Question

伙计们 - 我不知道是什么导致我的代码在这里中断，我希望你们能帮助找出原因!您在下面看到的函数从 Web 服务获取一行，并根据返回的数据构建一个表行。

    function GetData(id, thisRow) {
                    if (id == 0) {
                        var tier = 0;
                    }
                    else {
                        var currenttier = parseInt(thisRow.find("td.Tier").text());
                        var tier = currenttier + 1;
                    }
    //*** this console.log is affected by the for loop that appears later..
                    console.log(tier);
                    $.ajax({
                        type: "POST",
                        url: "F2.svc/GetChildTable",
                        data: id,
                        contentType: "application/json; charset=utf-8",
                        dataType: "json",
                        success: function (data, textStatus, xhr) {

                            var tempstring = "";
                            var temp = "";
                            if (data.Rows.length > 0) {
                                for (var i = 0; i < data.Rows.length; i++) {
                                    tempstring += "<tr class = 'Show Row ItemID-" + data.Rows[i].ItemID + " ParentID-" + data.Rows[i].ItemParentID + " Tier-" + tier + "'>";
                                    tempstring += "<td class='Tier'>";
    //*** the loop below seems to break the tier variable declared up above..             
                                   for (var p = 0; p < tier; p++) {
                                        tempstring += "+";
                                    }
                                    tempstring += " " + tier;
                                    tempstring += "</td>";
                                    tempstring += "<td class='ItemID'>";
                                    tempstring += data.Rows[i].ItemID;
                                    tempstring += "</td>";
                                    tempstring += "<td class='ItemParentID'>";
                                    tempstring += data.Rows[i].ItemParentID;
                                    tempstring += "</td>";
                                    tempstring += "<td class='ItemDateEntered'>";
                                    tempstring += data.Rows[i].ItemDateEntered;
                                    tempstring += "</td>";
                                    tempstring += "<td class='ItemLastUpdated'>";
                                    tempstring += data.Rows[i].ItemLastUpdated;
                                    tempstring += "</td>";
                                    tempstring += "<td class='ItemName'>";
                                    tempstring += data.Rows[i].ItemName;
                                    tempstring += "</td>";
                                    tempstring += "<td class='ItemStatusID'>";
                                    tempstring += data.Rows[i].ItemStatusID;
                                    tempstring += "</td>";
                                    tempstring += "<td class='ItemTasks'>";
                                    tempstring += data.Rows[i].ItemTasks;
                                    tempstring += "</td>";
                                    tempstring += "<td class='ItemBlocks'>";
                                    tempstring += data.Rows[i].ItemBlocks;
                                    tempstring += "</td>";
                                    tempstring += "<td class='ItemComments'>";
                                    tempstring += data.Rows[i].ItemComments;
                                    tempstring += "</td>";
                                    tempstring += "<td class='ItemFilterID'>";
                                    tempstring += data.Rows[i].ItemFilterID;
                                    tempstring += "</td>";
                                    tempstring += "<td class='ItemManHoursEst'>";
                                    tempstring += data.Rows[i].ItemManHoursEst;
                                    tempstring += "</td>";
                                    tempstring += "<td class='ItemManHoursAct'>";
                                    tempstring += data.Rows[i].ItemManHoursAct;
                                    tempstring += "</td><td></td>"
                                }
                                tempstring += "</tr>";

                                var newRow = $(tempstring);

                                if (id == 0) {
                                    $("table#Main > tbody").html(newRow);
                                }
                                else {
                                    thisRow.after(newRow);
                                    thisRow.addClass("ChildrenLoaded");
                                }
                            }
                        },
                        error: function (xhr, textStatus, ex) {
                            var response = xhr.responseText;
                            if (response.length > 11 && response.substr(0, 11) === '{"Message":' &&
                    response.charAt(response.length - 1) === '}') {
                                var exInfo = JSON.parse(xhr.responseText);
                                var text = "Message: " + exInfo.Message + "\r\n" +
                                "Exception: " + exInfo.ExceptionType; // + exInfo.StackTrace;
                                alert(text);
                            } else {
                                alert("error");
                            }
                        }
                    });
                }

正如你所看到的，console.log(tier) 在应该显示 2 的时候却显示了 NaN。真正奇怪的是，如果我注释掉包含 tempstring += "+"; 的 for 循环。 console.log 按您的预期工作。我能看到的唯一关系是 for 循环使用 p < tier 但这不应该对之前的 tier 变量声明产生任何影响，对吧？

哦，我想这也是不言而喻的 tempstring += ""+ tier;也坏了^^

谢谢!

Answer 1

大量代码，没有 HTML 转储，但我有一个猜测。

第一次尝试似乎运行良好，但是:

var currenttier = parseInt(thisRow.find("td.Tier").text());

之后会杀了你，因为你在每一层添加了一个 +:

console.log(parseInt('++ 1')); // NaN

您必须去掉加号，否则您的号码将无法解析。