Problem with Ionic 2 and extension of native Typescript type

Ionic Framework ionic-v3
1

I’ve the following project directory structure:

app
    ...
    extensions
        - array.ts
        - string.ts
    support
        - net.ts
    ...

Inside the file array.ts there is the following Array<T> interface extension:

Array.prototype.contains = function(element) {
    return this.indexOf(element) > -1; 
};

Array.prototype.containsIgnoreCase = function(element) {
    if(element == undefined) return false;
    for(let item of this)
        if(element.toString().toLowerCase() == item.toString().toLowerCase())
            return true;
    return false;
};

interface Array<T> {
    contains(element : T): boolean;
    containsIgnoreCase(element : any): boolean;
}

and inside the string.ts there is the following String interface extension:

String.prototype.containsNumber = function() {
    return /.*\d+.*/g.test(this);
};

String.prototype.toUTF8Array = function() {
    var str = unescape(encodeURIComponent(this)),
        charList = str.split(''),
        uintArray = [];
    for (var i = 0; i < charList.length; i++) {
        uintArray.push(charList[i].charCodeAt(0));
    }
    return new Uint8Array(uintArray);
};

interface String {
    containsNumber(): boolean;
    toUTF8Array(): Uint8Array;
}

In the file net.ts there are different parts of the code that access the above extension methods, for example:

let code = "<code>";
let byteArray = code.toUTF8Array();

but when I compile the code using ionic build the compiler throws the following errors:

TypeScript error: E:/<project dir>/app/support/net.ts(29,62): Error TS2339: Property 'contains' does not exist on type 'string[]'.
TypeScript error: E:/<project dir>/app/support/net.ts(35,20): Error TS2339: Property 'containsNumber' does not exist on type 'string'.
TypeScript error: E:/<project dir>/app/support/net.ts(88,49): Error TS2339: Property 'toUTF8Array' does not exist on type 'string'.
TypeScript error: E:/<project dir>/app/support/net.ts(89,81): Error TS2339: Property 'toUTF8Array' does not exist on type 'string'.

I read on internet that to extend a native type just write an interface with the name of the type to extend, leaving it in the global namespace and provide the implementations of the added methods (As I wrote before) … that’s it!! Right?

How can I solve the problem?

UPDATE

Creating a file named index.ts with the following content

export { } from './array';
export { } from './string';

and inserting this line of code

import { } from '../extensions';

at the start of the net.ts file, the compilation peforms succefully.
Now, there is another problem. When I exec the command ionic serve
and try to test the app with Google Chrome, the browser throws the following
error:

TypeError: support_1.Guid.newGuid(...).toUTF8Array is not a function

where Guid.newGuid(...) is a function that returns a string.

POSSIBLE SOLUTION

I opened the app.bundle.js inside the www/build/js folder and I figure out that the above described interface definitions and implementations was not present.

To solve the problem I modified the gulpfile.js in this way:

gulp.task('watch', ['clean'], function(done){
  runSequence(
    ['sass', 'html', 'fonts', 'scripts'],
    function(){
      gulpWatch('app/**/*.scss', function(){ gulp.start('sass'); });
      gulpWatch('app/**/*.html', function(){ gulp.start('html'); });
      buildBrowserify({
        src: [ <------ ADDED
          './app/extensions/array.ts', <------ ADDED
          './app/extensions/string.ts', <------ ADDED
          './app/app.ts', <------ ADDED
          './typings/index.d.ts' <------ ADDED
        ],
        watch: true 
      })
      .on('end', done);
    }
  );
});

and:

...
gulp.task('build', ['clean'], function(done){
runSequence(
    ['sass', 'html', 'fonts', 'scripts'],
    function(){
      buildBrowserify({
        src: [ <---- ADDED
          './app/extensions/array.ts', <------ ADDED
          './app/extensions/string.ts', <------ ADDED
          './app/app.ts', <------ ADDED
          './typings/index.d.ts' <------ ADDED
        ],
        minify: isRelease,
        browserifyOptions: {
          debug: !isRelease
        },
        uglifyOptions: {
          mangle: false
        }
      }).on('end', done);
    }
  );
});

Now both the commands ionic build and ionic serve work properly.