Why the use of `Function.prototype.run` inside Angular type script class is illegal-CodePudding

I would like to define globally new function called run inside my Angular component like so:

Function.prototype.run = function (delay: number) {
  // some content;
};

... but the compiler generates an error that the Property 'run' does not exist on type 'Function'. If I do the same code using just plain java script and compile it using node.js it compiles without any problems. Anybody knows why?

CodePudding user response：

It is generally not recommended to add properties to native JavaScript objects, but if you really want to do it, just leverage TypeScript's declaration merging:

declare global {
    interface Function {
        run: (delay: number) => void;
    }
}

Function.prototype.run = function (delay: number) {
  // some content;
};

TypeScript playground

CodePudding user response：

To make tsc leave you alone, just cast to any

(Function.prototype as any).run = function (delay: number) {
  // some content;
};

Or create a new type

type myType = Function & { run: Function };

(Function.prototype as myType).run = function (delay: number) {
  // some content;
};

You can also use the Object class to define new properties

Object.defineProperty(Function.prototype, 'run', {
  value: (delay: number) => {},
});