spservices.js.Error:- Uncaught (in > promise) TypeError: Cannot read properties of undefined (reading > 'LookupList')

Question

Inside our SPFx web part we have the following code inside the spservices.js code:-

spservices.prototype.getLookupFieldOptions = function (siteUrl, listId, fieldInternalName) { return __awaiter(this, void 0, void 0, function () { var fieldOptions, web, results, options, _i, options_1, option, error_14; return __generator(this, function (_a) { switch (_a.label) { case 0: fieldOptions = []; _a.label = 1; case 1: _a.trys.push([1, 5, , 6]); web = new Web(siteUrl); return [4 /*yield*/, web.lists.getById(listId) .fields.usingCaching() .filter("InternalName eq '" + fieldInternalName + "'") .select("LookupList", "LookupWebId", "LookupField") .top(1) .get()]; case 2: results = _a.sent(); if (!results) return [3 /*break*/, 4]; return [4 /*yield*/, web.lists.getById(results[0].LookupList) .items.usingCaching() .select("ID", results[0].LookupField) .getAll()]; case 3: options = _a.sent(); if (options && options.length > 0) { for (_i = 0, options_1 = options; _i < options_1.length; _i++) { option = options_1[_i]; fieldOptions.push({ key: option.ID, text: option[results[0].LookupField] }); } } _a.label = 4; case 4: return [3 /*break*/, 6]; case 5: error_14 = _a.sent(); return [2 /*return*/, Promise.reject(error_14)]; case 6: return [2 /*return*/, fieldOptions]; } }); }); }; 

but on runtime the SPFx web part will return this error and it will keep loading forever:-

calendar-web-part_a87ac4ce95dc9057c9f00ccd9727c133.js:1 Uncaught (in promise) TypeError: Cannot read properties of undefined (reading 'LookupList')

this is the piece of code which is returning the error:-

return [4 /*yield*/, web.lists.getById(results[0].LookupList) 

as follow:-

any advice on this please?

Answer 1

I believe the problem on that "Select" function, it is trying to read some sort of nested properties in each value.

TypeError: Cannot read properties of undefined (reading 'LookupList') : this error is thrown when the caller is expecting a "Promise" to be returned and instead it is receiving "undefined"

So I assume to replace what you want to return on variables like the following :

var SPListWithFilteredItems = web.lists.getById(listId).fields.usingCaching().filter("InternalName eq '"+ fieldInternalName + "'").select("LookUpList","LookupWebId","LookupField").top(1).get(); return SPListWithFilteredItems; 

Try one by one, at first try :

 web.lists.getById(listId) 

Then

web.lists.getById(listId).fields.usingCaching() 

Then

web.lists.getById(listId).fields.usingCaching().filter("InternalName eq '"+ fieldInternalName + "'") 

... etc and let me know of the results.

Cordially.