JS Call new Class().function1().function2() and keep "this"

Question

I have a problem with Class Javascript. I created class with constructor and two functions.

export default class Example {
  private image: string;
  private processedImage: Sharp | undefined;

  constructor(image: string) {
    this.image = image;
  }

  resize(): ResizeClb {
    this.processedImage = resizeImage(this.image, ...);

    return {
      merge: this.merge
    };
  }

  merge(images: MergeImages[]): void {
    console.log(this.processedImage); // print undefined 
    this.processedImage = this.processedImage.composite(layers);
  }
}

I want call chained functions:

const a = new Example(myImage).resize().merge(...othersImages);

But when I called the chained function I get undefined in this.processedImage line. I can't access to value of the class.

It's work if I not use chains functions.

const a = new Example(myImage);
a.resize();
a.merge(...othersImages); // It work.

It work but I required use chains functions. Thank you!