Tips for changing window.function in Typescript

Question

Tips for changing window.function in Typescript

I'm attempting to log when a method is automatically called. (I found the code snippet on )

augment(withFn) {
        let name, fn;
        for (name in window) {
            fn = window[name];
            if (typeof fn === 'function') {               
                window[name] = (function(n, f) {   // An error is occurring here.
                    const args = arguments;
                    return function() {
                        withFn.apply(this, args);
                        return fn.apply(this, arguments);
                    };
                })(name, fn);
            }
        }
    }

and then call this.

this.augment(function(name, fn) {
        console.log('calling ' + name);
    });

An error is being thrown:

ERROR in src/app/app.component.ts(81,17): error TS2740: Type '() => any' is missing the following properties from type 'Window': Blob, TextDecoder, TextEncoder, URL, and 232 more.

I'm wondering how I can override a window function?

typescript callback

Answer 1

Answer №1

When working with TypeScript, the window[name] property is treated as a member of the Window interface which should include objects like Blob, TextDecoder, and TextEncoder.

This behavior is due to the fact that the Window interface contains a dynamic property definition:

interface Window extends EventTarget, WindowTimers, ... {
  ...
  [index: number]: Window;
}

which allows for referencing window objects in frames such as window[0], window[1], and so on.

To address this issue, you can extend the existing Window interface to handle your scenario:

declare global {
  interface Window {
    [index: string]: () => any; // or simply 'any'
  }
}

Additionally, ensure that the variable let name is explicitly declared as type string:

let name: string

Below is the complete code snippet:

app.component.ts

export class AppComponent {
  ...

  ngOnInit() {
    this.augment(function(name, fn) {
        console.log('calling ' + name);
    });
  }

  augment(withFn) {
    let name: string, fn;
    for (name in window) {
      fn = window[name];
      if (typeof fn === 'function') {
        window[name] = (function (n, f) {
          const args = arguments;
          return function () {
            withFn.apply(this, args);
            return fn.apply(this, arguments);
          };
        })(name, fn);
      }
    }
  }
}

declare global {
  interface Window {
    [index: string]: () => any;
  }
}

Note: There are simpler ways to resolve TypeScript errors:

Ignore an error:

// @ts-ignore
window[name] = (function(n, f) {

Use the any keyword:

(window[name] as any) = (function(n, f) {

or

(<any>window[name]) = (function (n, f) {

Answer 2

When working with TypeScript, the window[name] property is treated as a member of the Window interface which should include objects like Blob, TextDecoder, and TextEncoder.

This behavior is due to the fact that the Window interface contains a dynamic property definition:

interface Window extends EventTarget, WindowTimers, ... {
  ...
  [index: number]: Window;
}

which allows for referencing window objects in frames such as window[0], window[1], and so on.

To address this issue, you can extend the existing Window interface to handle your scenario:

declare global {
  interface Window {
    [index: string]: () => any; // or simply 'any'
  }
}

Additionally, ensure that the variable let name is explicitly declared as type string:

let name: string

Below is the complete code snippet:

app.component.ts

export class AppComponent {
  ...

  ngOnInit() {
    this.augment(function(name, fn) {
        console.log('calling ' + name);
    });
  }

  augment(withFn) {
    let name: string, fn;
    for (name in window) {
      fn = window[name];
      if (typeof fn === 'function') {
        window[name] = (function (n, f) {
          const args = arguments;
          return function () {
            withFn.apply(this, args);
            return fn.apply(this, arguments);
          };
        })(name, fn);
      }
    }
  }
}

declare global {
  interface Window {
    [index: string]: () => any;
  }
}

Note: There are simpler ways to resolve TypeScript errors:

Ignore an error:

// @ts-ignore
window[name] = (function(n, f) {

Use the any keyword:

(window[name] as any) = (function(n, f) {

or

(<any>window[name]) = (function (n, f) {

Tips for changing window.function in Typescript

Answer №1

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