An example to demonstrate the usage of Symbol.toPrimitive

Symbol.js

// Taken from https://h3manth.com/posts/Well-known-symbols/
class Life {
  [Symbol.toPrimitive](hint) {
    switch (hint) {
      case "number":
        return 100;
      case "string":
        return "Hundred";
      case "default":
        return true;
    }
  }
}

const myLife = new Life();
console.log(+myLife); // 100
console.log(`${myLife}`); // "Hundred"
console.log(myLife + 0); // 1

Without the Symbol.toPrimitive the output will be

 NaN 
[object Object] 
[object Object]0