Error when concatenating String[] in Angular 2

Question

I am trying to concatenate two Strings in typescript as follows:

//This array is declared as a class variable 
testArray: String[] = ['first', second', 'third'];

concatArray(): void {
    var testString = new String("");
    this.testArray.forEach((item, index) => {
        testString = testString.concat(item);
    });
    console.log(testString);
}

When run the console.log will output the correct value: 'firstsecondthird'

However i get a compile error which says:

error TS2345: Argument of type 'String' is not assignable to parameter of type 'string'.
  'string' is a primitive, but 'String' is a wrapper object.
  Prefer using 'string' when possible.

I don't understand this error as both the testArray and the testString both seem to be of type String?

I'm new to typescript. Could somebody point out what is problem here?

Have you tried to use the lowercase `string` type, i.e. `string[]` instead of `String[]` and to then not use `new String(...)` syntax. — Daniel W Strimpel, Apr 08 '18 at 13:42
Have you looked at this? https://stackoverflow.com/questions/14727044/typescript-difference-between-string-and-string — Daniel W Strimpel, Apr 08 '18 at 13:44
ideally you should use - var testString = testArray.join(); rather than looping/iterating over string array. — Sumit Deshpande, Apr 08 '18 at 15:57

Error when concatenating String[] in Angular 2

0 Answers0