let spaceship = {
homePlanet : 'Earth',
color : 'red'
};
let tryReassignment = obj => {
obj = {
identified : false,
'transport type' : 'flying'
}
console.log(obj) // Prints {'identified': false, 'transport type': 'flying'}
};
tryReassignment(spaceship) // The attempt at reassignment does not work.
spaceship // Still returns {homePlanet : 'Earth', color : 'red'};
spaceship = {
identified : false,
'transport type': 'flying'
}; // Regular reassignment still works.Let’s look at what happened in the code example:
We declared this spaceship object with let. This allowed us to reassign it to a new object with identified and 'transport type' properties with no problems. When we tried the same thing using a function designed to reassign the object passed into it, the reassignment didn’t stick (even though calling console.log() on the object produced the expected result). When we passed spaceship into that function, obj became a reference to the memory location of the spaceship object, but not to the spaceship variable. This is because the obj parameter of the tryReassignment() function is a variable in its own right. The body of tryReassignment() has no knowledge of the spaceship variable at all! When we did the reassignment in the body of tryReassignment(), the obj variable came to refer to the memory location of the object {'identified' : false, 'transport type' : 'flying'}, while the spaceship variable was completely unchanged from its earlier value.
