ionic2 typescript compilation error for adding a method to String or Number

Question

In my Ionic2 project, I am trying to add a new method to Number as in the following code.

interface StringConstructor {
  bar(msg: string): void;
}

String.bar = function(msg: string) {
  alert("Example of static extension: " + msg);
}

String.bar("Hello World");


interface NumberConstructor {
  toRad(): number;
}

Number.toRad = function() { return this * (Math.PI / 180); }; 

export function gpsDist() {
  
}

When I do ionic build, it gives me the following errors:

TypeScript error: /Users/cju/Projects/Bus2-App/app/util/mathUtil.ts(7,8): Error TS2339: Property 'bar' does not exist on type 'StringConstructor'.

TypeScript error: /Users/cju/Projects/Bus2-App/app/util/mathUtil.ts(11,8): Error TS2339: Property 'bar' does not exist on type 'StringConstructor'.

TypeScript error: /Users/cju/Projects/Bus2-App/app/util/mathUtil.ts(18,8): Error TS2339: Property 'toRad' does not exist on type 'NumberConstructor'.

However the same file compiles ok outside ionic. If I compile it with tsc, I get no errors. All the code are in one file.

I tried to compile the file outside "ionic build" command by doing "node tsc.js myfile.ts" and "node typescript.js myfile.ts", both compile without error. The tsc.js and typescript.js come from ionic-gulp-browserify-typescript/node_modules/tsify/node_modules/typescript/lib. — Charles Ju
– Charles Ju, Commented May 18, 2016 at 9:10

Community · Accepted Answer · 2017-05-23 12:16:03Z

0

Angular takes care of ts compilation, you can edit the typescript compiler options in the file tsconfig.json which is in the root of your app. But I don't think you want to mess with that.

Try the non-static way to extend functionality that you can find here: https://stackoverflow.com/a/13897813/1016128

edited May 23, 2017 at 12:16

CommunityBot

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answered May 18, 2016 at 10:11

Manu Valdés

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1 Comment

Charles Ju Over a year ago

I did this. interface Number { toRad(): number; } Number.prototype.toRad = function() { return this * 2; }; It still gives me the error "Error TS2339: Property 'toRad' does not exist on type 'Number'." But it still runs and gives me the correct result.

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