var pvalue = 'foo';

​

var ovalue = {

  foo : 'foo'

};

​

changeMe( pvalue, ovalue );

​

console.log( pvalue, ovalue );

​

reassignMe( ovalue );

​

console.log( ovalue );

​

function changeMe( primitive, obj ){

  primitive = 'bar';

  obj.foo = 'bar';

}

​

function reassignMe( obj ) {

  obj = {

    baz : 'baz'

  };

}