好像漏了两行。您可以尝试下面修改后的版本吗？

// Model data in format for charts
class ModelData {
    constructor(viewer) {
        this._modelData = {};
        this._viewer = viewer;
    }

    init(callback) {
        var _this = this;
        var viewer = _this._viewer;

        _this.getAllLeafComponents(function (dbIds) {
            var count = dbIds.length;
            dbIds.forEach(function (dbId) {
                viewer.getProperties(dbId, function (props) {
                    props.properties.forEach(function (prop) {
                        if (!isNaN(prop.displayValue)) return; // let's not categorize properties that store numbers

                        // some adjustments for revit:
                        prop.displayValue = prop.displayValue.replace('Revit ', ''); // remove this Revit prefix
                        if (prop.displayValue.indexOf('<') == 0) return; // skip categories that start with <

                        // ok, now let's organize the data into this hash table
                        if (_this._modelData[prop.displayName] == null) _this._modelData[prop.displayName] = {};
                        if (_this._modelData[prop.displayName][prop.displayValue] == null) _this._modelData[prop.displayName][prop.displayValue] = [];
                        _this._modelData[prop.displayName][prop.displayValue].push(dbId);
                    })
                    if ((--count) == 0) callback();
                });
            })
        })
    }

    getAllLeafComponents(callback) {
        var _this = this;
        var viewer = _this._viewer;
        // from https://learnforge.autodesk.io/#/viewer/extensions/panel?id=enumerate-leaf-nodes
        viewer.getObjectTree(function (tree) {
            var leaves = [];
            tree.enumNodeChildren(tree.getRootId(), function (dbId) {
                if (tree.getChildCount(dbId) === 0) {
                    leaves.push(dbId);
                }
            }, true);
            callback(leaves);
        });
    }

    hasProperty(propertyName){
        return (this._modelData[propertyName] !== undefined);
    }

    getLabels(propertyName) {
        return Object.keys(this._modelData[propertyName]);
    }

    getCountInstances(propertyName) {
        return Object.keys(this._modelData[propertyName]).map(key => this._modelData[propertyName][key].length);
    }

    getIds(propertyName, propertyValue) {
        return this._modelData[propertyName][propertyValue];
    }
}