reassignment.js

var a = [1, 2, 3];

function doSomething(b){ // the parameter `b` that corresponds to the argument `a` is a copy of a reference to the array a
  b = [2]; //if we change b via reassignment inside a function or outside of the function, that reassignment does not affect a
  console.log(b) // [2]
}

doSomething(a); 

console.log(a) // [1, 2, 3]