error TS2554: Expected 1 arguments, but got 0. Angular6

I do not see any issue with your code, as i see you should stop the applicaiton with Ctrl + C

and then do ng serve

Anyhow the reason being is that, your getEmployee method still needs one parameter to be passed, just make sure your code is saved on the service part.

It seems to be related to the new Angular compiler option fullTemplateTypeCheck, if that option is set to true in the tsconfig file, the error appears.

Here is an example of the tsconfig.app.json file that reproduces the build error:

{  
  "extends": "../tsconfig.json",  
  "compilerOptions": {  
    "outDir": "../out-tsc/app",  
    "baseUrl": "./",  
    "module": "es2015",  
    "types": []  
  },

  "angularCompilerOptions": {  
     "fullTemplateTypeCheck": true  
  },  
  "exclude": [  
    "test.ts",  
    "**/*.spec.ts"  
  ]  
}