Angular CLI - Typescript throws: Unable to read property length undefined

Question

I am running an angular 4 project using ng serve and getting an error

Cannot read property 'length' of undefined 

but I have no property length in my project.

complete mistake

  Your global Angular CLI version (1.2.1) is greater than your local version (1.1.3). The local Angular CLI version is used. To disable this warning use "ng set --global warnings.versionMismatch=false". Cannot read property 'length' of undefined TypeError: Cannot read property 'length' of undefined at createSourceFile (E:\פרוייקטים\פרוייקטים קיץ\Angular 4\Youtube Channel Angular Firebase\full project of the instructor github\angular-firestarter-master\node_modules\typescript\lib\typescript.js:15457:109) at parseSourceFileWorker (E:\פרוייקטים\פרוייקטים קיץ\Angular 4\Youtube Channel Angular Firebase\full project of the instructor github\angular-firestarter-master\node_modules\typescript\lib\typescript.js:15389:26) at Object.parseSourceFile (E:\פרוייקטים\פרוייקטים קיץ\Angular 4\Youtube Channel Angular Firebase\full project of the instructor github\angular-firestarter-master\node_modules\typescript\lib\typescript.js:15338:26) at Object.createSourceFile (E:\פרוייקטים\פרוייקטים קיץ\Angular 4\Youtube Channel Angular Firebase\full project of the instructor github\angular-firestarter-master\node_modules\typescript\lib\typescript.js:15192:29) at VirtualFileStats.getSourceFile (E:\פרוייקטים\פרוייקטים קיץ\Angular 4\Youtube Channel Angular Firebase\full project of the instructor github\angular-firestarter-master\node_modules\@ngtools\webpack\src\compiler_host.js:66:35) at WebpackCompilerHost.getSourceFile (E:\פרוייקטים\פרוייקטים קיץ\Angular 4\Youtube Channel Angular Firebase\full project of the instructor github\angular-firestarter-master\node_modules\@ngtools\webpack\src\compiler_host.js:213:38) at findSourceFile (E:\פרוייקטים\פרוייקטים קיץ\Angular 4\Youtube Channel Angular Firebase\full project of the instructor github\angular-firestarter-master\node_modules\typescript\lib\typescript.js:67909:29) at processImportedModules (E:\פרוייקטים\פרוייקטים קיץ\Angular 4\Youtube Channel Angular Firebase\full project of the instructor github\angular-firestarter-master\node_modules\typescript\lib\typescript.js:68056:25) at findSourceFile (E:\פרוייקטים\פרוייקטים קיץ\Angular 4\Youtube Channel Angular Firebase\full project of the instructor github\angular-firestarter-master\node_modules\typescript\lib\typescript.js:67937:17) at processImportedModules (E:\פרוייקטים\פרוייקטים קיץ\Angular 4\Youtube Channel Angular Firebase\full project of the instructor github\angular-firestarter-master\node_modules\typescript\lib\typescript.js:68056:25) at findSourceFile (E:\פרוייקטים\פרוייקטים קיץ\Angular 4\Youtube Channel Angular Firebase\full project of the instructor github\angular-firestarter-master\node_modules\typescript\lib\typescript.js:67937:17) at processSourceFile (E:\פרוייקטים\פרוייקטים קיץ\Angular 4\Youtube Channel Angular Firebase\full project of the instructor github\angular-firestarter-master\node_modules\typescript\lib\typescript.js:67840:27) at processRootFile (E:\פרוייקטים\פרוייקטים קיץ\Angular 4\Youtube Channel Angular Firebase\full project of the instructor github\angular-firestarter-master\node_modules\typescript\lib\typescript.js:67728:13) at E:\פרוייקטים\פרוייקטים קיץ\Angular 4\Youtube Channel Angular Firebase\full project of the instructor github\angular-firestarter-master\node_modules\typescript\lib\typescript.js:67018:60 at Object.forEach (E:\פרוייקטים\פרוייקטים קיץ\Angular 4\Youtube Channel Angular Firebase\full project of the instructor github\angular-firestarter-master\node_modules\typescript\lib\typescript.js:1449:30) at Object.createProgram (E:\פרוייקטים\פרוייקטים קיץ\Angular 4\Youtube Channel Angular Firebase\full project of the instructor github\angular-firestarter-master\node_modules\typescript\lib\typescript.js:67018:16) PS E:\פרוייקטים\פרוייקטים קיץ\Angular 4\Youtube Channel Angular Firebase\full project of the instructor github\angular-firestarter-master> 

package.json

 { "name": "firestarter", "version": "0.0.0", "license": "MIT", "scripts": { "ng": "ng", "start": "ng serve", "build": "ng build", "test": "ng test", "lint": "ng lint", "e2e": "ng e2e" }, "private": true, "dependencies": { "@angular/animations": "^4.2.4", "@angular/common": "^4.2.4", "@angular/compiler": "^4.2.4", "@angular/core": "^4.2.4", "@angular/forms": "^4.2.4", "@angular/http": "^4.2.4", "@angular/platform-browser": "^4.2.4", "@angular/platform-browser-dynamic": "^4.2.4", "@angular/platform-server": "^4.2.4", "@angular/router": "^4.2.4", "@types/lodash": "^4.14.67", "angularfire2": "^4.0.0-rc.1", "core-js": "^2.4.1", "firebase": "^4.1.3", "lodash": "^4.17.4", "rxjs": "^5.4.1", "zone.js": "^0.8.12" }, "devDependencies": { "@angular/cli": "^1.1.3", "@angular/compiler-cli": "^4.2.4", "@types/jasmine": "2.5.53", "@types/node": "~8.0.4", "codelyzer": "~3.1.1", "jasmine-core": "~2.6.4", "jasmine-spec-reporter": "~4.1.1", "karma": "~1.7.0", "karma-chrome-launcher": "~2.2.0", "karma-cli": "~1.0.1", "karma-coverage-istanbul-reporter": "^1.3.0", "karma-jasmine": "~1.1.0", "karma-jasmine-html-reporter": "^0.2.2", "protractor": "~5.1.2", "ts-node": "~3.1.0", "tslint": "~5.4.3", "typescript": "=2.3.4" } } 

Answer 1

You may be missing one or more files that typescript is trying to process. To find out which file you are missing, simply add

console.log (file_name);

when the createSourceFile function is createSourceFile in the node_modules / typescript / lib / typescript.js file.

Answer 2

Most likely, you have modified your modules so that the CLI is restarted.

I had an error with the ng serve error after removing the component from the module. By restarting this process and restarting ng serve , the error disappeared.

Answer 3

My problem was that for some reason my envioroment.ts file was missing. Therefore, check the important files.

Answer 4

My error was caused by a c & p error when creating a small component. I forgot to change the path to the component template and styles.

Answer 5

I solved this problem (error during refactoring test). Everything is good for corner v4.3. * And v4.4 *

1. Change @angular/cli version 1.7.3 to 1.4.10 in package.json (latest version for angular4)
2. rm -rf node_modules
3. npm install --no-optional

Answer 6

In my case, I did the following and this solved the problem:

1. Create the environments folder (if it does not exist) in the src of the project C:\Users\abcd\Desktop\MyApp\src

2. Place the two files environment.ts and environment.prod.ts in the Environment folder.