作用域问题引发的血案

最近做项目过程中需要根据JSON数据生成一个树状的目录，结果代码如下：

var folderList=[
    {
        "FolderName": "ASD",
        "ChildList": null
    },
    {
        "FolderName": "内网公告",
        "ChildList": null
    },
    {
        "FolderName": "测试文档",
        "ChildList": null
    },
    {
        "FolderName": "软件开发",
        "ChildList": null
    },
    {
        "FolderName": "Test",
        "ChildList": [
            {
                "FolderName": "Test2",
                "ChildList": [
                    {
                        "FolderName": "Test3",
                        "ChildList": null
                    }
                ]
            }
        ]
    },
    {
        "FolderName": "个人",
        "ChildList": null
    },
    {
        "FolderName": "公司通知",
        "ChildList": null
    },
    {
        "FolderName": "采购平台",
        "ChildList": null
    }
];
            var str='';
            function generateFolders(arr) {
                if (arr.length > 0) {
                    str += '<div class="sui-list sui-list-icon ubt bc-gra1">';
                    for (var i = 0, len = arr.length; i < len; i++) {
                        str += '<ul class="ub ub-ac">' 

                                + '<li class="sui-list-licon sui-icon-ok-circle fts2">' + '</li>' 

                                + '<ul class="ub ub-f1 sui-list-item">' 

                                  + '<li class="ub-f1 sui-list-text sui-list-nowrap">' + arr[i].FolderName + '</li>' 

                                  + '<li class="sui-list-ricon ub-img sui-icon-chevron-right fts2"></li>' 

                                + '</ul>' 

                             + '</ul>';
                        if (isDefine(arr[i].ChildList)) {
                            str += generateFolders(arr[i].ChildList);
                        }
                    }
                    str += '</div>';
                    return str;
                }else{
                    return '';
                }
            }

            var folderTxt ='<div class="sui-list sui-list-icon ubt bc-gra1">' 
                                  +'<ul class="ub ub-ac">' 
                                      +'<li class="sui-list-licon sui-icon-drawer fts2">' + '</li>' 
                                      +'<ul class="ub ub-f1 sui-list-item">' 
                                          +'<li class="ub-f1 sui-list-text sui-list-nowrap">我的目录</li>' 
                                          +'<li class="sui-list-ricon ub-img sui-icon-chevron-right fts2"></li>' 
                                      +'</ul>' 
                                  +'</ul>';
            folderTxt+=generateFolders(folderList);
            folderTxt += '</div>';
            $('#list').html(folderTxt);

            /**
             * 判断是否是空
             * @param value
             */
            function isDefine(value){
                if(value == null || value == "" || value == "undefined" || value == undefined || value == "null" || value == "(null)" || value == 'NULL' || typeof(value) == 'undefined'){
                    return false;
                }
                else{
              value = value+"";
                    value = value.replace(/s/g,"");
                    if(value == ""){
                        return false;
                    }
                    return true;
                }
            }

结果出来的树如下图：

经排查，发现是由于str定义的位置不对引起的，将str定义为局部变量就可以了。

function generateFolders(arr) {
                var str='';
                if (arr.length > 0) {
                    str += '<div class="sui-list sui-list-icon ubt bc-gra1">';
                    for (var i = 0, len = arr.length; i < len; i++) {
                        str += '<ul class="ub ub-ac">' 
                                + '<li class="sui-list-licon sui-icon-ok-circle fts2"></li>' 
                                + '<ul class="ub ub-f1 sui-list-item">' 
                                    + '<li class="ub-f1 sui-list-text sui-list-nowrap">' + arr[i].FolderName + '</li>' 
                                    + '<li class="sui-list-ricon ub-img sui-icon-chevron-right fts2"></li>' 
                                + '</ul>' 
                            + '</ul>';
                        if (isDefine(arr[i].ChildList)) {
                            str += generateFolders(arr[i].ChildList);
                        }
                    }
                    str += '</div>';
                    return str;
                }else{
                    return '';
                }
            }

修改之后，可实现想的效果：