running npm server produces error

[daveharmswebdev]

c:\git-repositories\github\ngrx-course>npm run server

angular-ngrx-course@0.0.0 server c:\git-repositories\github\ngrx-course
ts-node -P ./server/server.tsconfig.json ./server/server.ts

c:\git-repositories\github\ngrx-course\node_modules\ts-node\src\index.ts:307
throw new TSError(formatDiagnostics(diagnosticList, cwd, ts, lineOffset))
^
TSError: ⨯ Unable to compile TypeScript
server\search-lessons.route.ts (19,35): Argument of type 'string | ParsedQs | string[] | ParsedQs[]' is not assignable to parameter of type 'string'.
Type 'ParsedQs' is not assignable to type 'string'. (2345)
server\search-lessons.route.ts (20,33): Argument of type 'string | ParsedQs | string[] | ParsedQs[]' is not assignable to parameter of type 'string'.
Type 'ParsedQs' is not assignable to type 'string'. (2345)
server\search-lessons.route.ts (22,63): This condition will always return 'false' since the types 'number' and 'string | ParsedQs | string[] | ParsedQs[]' have no overlap. (2367)
server\search-lessons.route.ts (25,102): Property 'toLowerCase' does not exist on type 'string | ParsedQs | string[] | ParsedQs[]'.
Property 'toLowerCase' does not exist on type 'string[]'. (2339)
at getOutput (c:\git-repositories\github\ngrx-course\node_modules\ts-node\src\index.ts:307:15)
at c:\git-repositories\github\ngrx-course\node_modules\ts-node\src\index.ts:336:16
at Object.compile (c:\git-repositories\github\ngrx-course\node_modules\ts-node\src\index.ts:496:11)
at Module.m._compile (c:\git-repositories\github\ngrx-course\node_modules\ts-node\src\index.ts:392:43)
at Module._extensions..js (internal/modules/cjs/loader.js:1157:10)
at Object.require.extensions. [as .ts] (c:\git-repositories\github\ngrx-course\node_modules\ts-node\src\index.ts:395:12)
at Module.load (internal/modules/cjs/loader.js:985:32)
at Function.Module._load (internal/modules/cjs/loader.js:878:14)
at Module.require (internal/modules/cjs/loader.js:1025:19)
at require (internal/modules/cjs/helpers.js:72:18)
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! angular-ngrx-course@0.0.0 server: ts-node -P ./server/server.tsconfig.json ./server/server.ts
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the angular-ngrx-course@0.0.0 server script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

npm ERR! A complete log of this run can be found in:
npm ERR! C:\Users\DHarms\AppData\Roaming\npm-cache_logs\2020-07-30T11_26_50_778Z-debug.log

c:\git-repositories\github\ngrx-course>

[daveharmswebdev]

this is a windows pc with the latest verison of Node

[daveharmswebdev]

this is in the 1-start branch

[daveharmswebdev]

solved it by adding toString in three places

import {Request, Response} from 'express';
import {LESSONS} from "./db-data";
import {setTimeout} from "timers";



export function searchLessons(req: Request, res: Response) {

    console.log('Searching for lessons ...');

        const queryParams = req.query;

        const courseId = queryParams.courseId,
            filter = queryParams.filter || '',
            sortOrder = queryParams.sortOrder || 'asc',
            pageNumber = parseInt(queryParams.pageNumber.toString()) || 0, // added toString() here
            pageSize = parseInt(queryParams.pageSize.toString()); // added toString() here

        let lessons = Object.values(LESSONS).filter(lesson => lesson.courseId === +courseId).sort((l1, l2) => l1.id - l2.id);

        if (filter) {
            lessons = lessons.filter(lesson => lesson.description.trim().toLowerCase().search(filter.toString().toLowerCase()) >= 0); // added toString() here
        }

        if (sortOrder === 'desc') {
            lessons = lessons.reverse();
        }

        const initialPos = pageNumber * pageSize;

        console.log(`Retrieving lessons page starting at position ${initialPos}, page size ${pageSize} for course ${courseId}`);

        const lessonsPage = lessons.slice(initialPos, initialPos + pageSize);

        res.status(200).json(lessonsPage);

}

[kshab]

Also you have transformed string to number (+courseId) in line 25. I've encountered the same issue. Thanks!