Javascript call Parent constructor in the Child (prototypical inheritance) - How it works? -

i know works, don't know why , how. mechanics?

// parent constructor function parent(name){   this.name = name || "the name property empty"; }  // child constructor function child(name){   this.name = name; }  // originaly, child "inherit" parent, name property, in case // shadowing name property in child constructor. child.prototype = new parent();  // want this: if dont set name, please inherit "the name property empty"  // parent constructor. know, doesn't work because shadow in child. var child1 = new child("laura"); var child2 = new child();  //and result undefined (of course)  console.log(child1.name, child2.name);  //"laura", undefined 

i know need, call() or apply() method. call "super class" (the parent constructor) child, , pass this object , argument name that. works:

function parent(name){   this.name = name || "the name property empty"; }  function child(name){   // call "super class" do? how work? don't understand process, lost line.   parent.call(this, name); }  child.prototype = new parent();  var child1 = new child("laura"); var child2 = new child();  console.log(child1.name, child2.name); // "laura", "the name property empty" 

it works perfectly, don't understand happens. lost this in mind, , can't follow process of call() method. copy constructor body parent child or what? , this object? why work?

please , describe process, don't understand.

first of all, stop doing child.prototype = new parent(); inheritance, unless browser doesn't support other alternative. that's bad style , can have undesired side effects, since runs constructor logic.

you can use object.create in every modern browser now.

child.prototype = object.create(parent.prototype); 

please note after should fix constructor property of child.prototype correctly points child rather parent.

child.prototype.constructor = child; 

next, how call works? call allows specify object referenced this keyword when function executed.

function child(name){   //when calling new child(...), 'this' references newly created 'child' instance    //we apply 'parent' constructor logic 'this', calling 'parent' function   //using 'call', allow specify object 'this' should reference    //during function execution.   parent.call(this, name); }