About function chaining in Javascript

animal.js

class Animal {
  constructor() {
    this.pace = null;
  }
  
  walk() {
    this.pace = "walking";
    
    console.log('our animal is', this.pace);
    
    return this;
  }
  
  run() {
    this.pace = "running";
    
    console.log('our animal is', this.pace);
    
    return this;
  }
}

let ourAnimal = new Animal();

ourAnimal.walk() // -> our animal is walking
ourAnimal.run() // -> our animal is running
ourAnimal.walk().run().walk().run()