javascript - Why is this prototype field taking precedence over the same object field? -

i'm in process of learning javascript prototypes , trying understand why happening. it's understanding when looking value of property, object checked before prototype. when then, print "brown"?

function box(item) {     this.item = item; }  box.prototype.color = "brown"; box.color = "blue";  var box = new box(null); console.log(box.color);  >>> brown 

box.color = "blue"; assigns property function box, not instance of it. can verify running console.dir(box) , console.dir(box).

if want assign property instance, have create instance first:

box.prototype.color = "brown";  var box = new box(null); box.color = "blue" 

or assign inside constructor function:

function box(item) {     this.item = item;     this.color = 'blue'; }