reference.js

// See https://stackoverflow.com/questions/13104494/does-javascript-pass-by-reference

(function(){
  var foo = [
    'hello'
  ];

  var replace_the_argument = function (some_array) {
    some_array = ['hola'];
    return some_array;
  };

  console.log('result of replace_the_argument():');
  console.log(replace_the_argument(foo));
  
  console.log('original:');
  console.log(foo);

})();

(function(){
  var foo = [
    'hello'
  ];

  var mutate_the_argument = function (some_array) {
    some_array.push('goodbye');
    return some_array;
  };
  
  console.log('result of mutate_the_argument():');
  console.log(mutate_the_argument(foo));
  
  console.log('original:');
  console.log(foo);

})();

Result:

$ node reference.js
result of replace_the_argument():
[ 'hola' ]
original:
[ 'hello' ]
result of mutate_the_argument():
[ 'hello', 'goodbye' ]
original:
[ 'hello', 'goodbye' ]