Search code examples
javascriptcoerciontemplate-literals

JavaScript template literals and implicit coercion

What value should be assigned to "x" in order to meet the following condition: 

// let x = ?; 

console.log(`${x}` != '' + x) // true
console.log(`${x}` !== '' + x) // true
Solution

  • Something like this can work, but it is tricky, the method toString() of the x object changes his internal state on every call and returns it. This happens because of the implicit coercion that takes effect when trying to cast x to a string (it will use the toString() method of the object if found).

    let x = {
  counter: 1,
  toString: () => x.counter++
}

console.log('' + x);
console.log(`${x}`);

console.log(`${x}` != '' + x) // true
console.log(`${x}` !== '' + x) // true