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Inheritance in Javascript

// define the Person Class
function Person() {}
 
Person.prototype.walk = function(){
  alert ('I am walking!');
};
Person.prototype.sayHello = function(){
  alert ('hello');
};
 
// define the Student class
function Student() {
  // Call the parent constructor
  Person.call(this);
}
 
// inherit Person
Student.prototype = new Person();
 
// correct the constructor pointer because it points to Person
Student.prototype.constructor = Student;
  
// replace the sayHello method
Student.prototype.sayHello = function(){
  alert('hi, I am a student');
}
 
// add sayGoodBye method
Student.prototype.sayGoodBye = function(){
  alert('goodBye');
}
 
var student = new Student();
student.sayHello();
student.walk();
student.sayGoodBye();
 
// check inheritance
alert(student instanceof Person); // true 
alert(student instanceof Student); // true
https://snipt.net/embed/519f9e611d12fc9c76a451be532d5ce9/
/raw/519f9e611d12fc9c76a451be532d5ce9/
519f9e611d12fc9c76a451be532d5ce9
js
JavaScript
40
2019-05-25T10:15:33
True
False
False
Oct 08, 2012 at 01:15 PM
/api/public/snipt/48249/
inheritance-in-javascript
<table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre><a href="#L-1"> 1</a> <a href="#L-2"> 2</a> <a href="#L-3"> 3</a> <a href="#L-4"> 4</a> <a href="#L-5"> 5</a> <a href="#L-6"> 6</a> <a href="#L-7"> 7</a> <a href="#L-8"> 8</a> <a href="#L-9"> 9</a> <a href="#L-10">10</a> <a href="#L-11">11</a> <a href="#L-12">12</a> <a href="#L-13">13</a> <a href="#L-14">14</a> <a href="#L-15">15</a> <a href="#L-16">16</a> <a href="#L-17">17</a> <a href="#L-18">18</a> <a href="#L-19">19</a> <a href="#L-20">20</a> <a href="#L-21">21</a> <a href="#L-22">22</a> <a href="#L-23">23</a> <a href="#L-24">24</a> <a href="#L-25">25</a> <a href="#L-26">26</a> <a href="#L-27">27</a> <a href="#L-28">28</a> <a href="#L-29">29</a> <a href="#L-30">30</a> <a href="#L-31">31</a> <a href="#L-32">32</a> <a href="#L-33">33</a> <a href="#L-34">34</a> <a href="#L-35">35</a> <a href="#L-36">36</a> <a href="#L-37">37</a> <a href="#L-38">38</a> <a href="#L-39">39</a> <a href="#L-40">40</a></pre></div></td><td class="code"><div class="highlight"><pre><span></span><span id="L-1"><a name="L-1"></a><span class="c1">// define the Person Class</span> </span><span id="L-2"><a name="L-2"></a><span class="kd">function</span> <span class="nx">Person</span><span class="p">()</span> <span class="p">{}</span> </span><span id="L-3"><a name="L-3"></a> </span><span id="L-4"><a name="L-4"></a><span class="nx">Person</span><span class="p">.</span><span class="nx">prototype</span><span class="p">.</span><span class="nx">walk</span> <span class="o">=</span> <span class="kd">function</span><span class="p">(){</span> </span><span id="L-5"><a name="L-5"></a> <span class="nx">alert</span> <span class="p">(</span><span class="s1">&#39;I am walking!&#39;</span><span class="p">);</span> </span><span id="L-6"><a name="L-6"></a><span class="p">};</span> </span><span id="L-7"><a name="L-7"></a><span class="nx">Person</span><span class="p">.</span><span class="nx">prototype</span><span class="p">.</span><span class="nx">sayHello</span> <span class="o">=</span> <span class="kd">function</span><span class="p">(){</span> </span><span id="L-8"><a name="L-8"></a> <span class="nx">alert</span> <span class="p">(</span><span class="s1">&#39;hello&#39;</span><span class="p">);</span> </span><span id="L-9"><a name="L-9"></a><span class="p">};</span> </span><span id="L-10"><a name="L-10"></a> </span><span id="L-11"><a name="L-11"></a><span class="c1">// define the Student class</span> </span><span id="L-12"><a name="L-12"></a><span class="kd">function</span> <span class="nx">Student</span><span class="p">()</span> <span class="p">{</span> </span><span id="L-13"><a name="L-13"></a> <span class="c1">// Call the parent constructor</span> </span><span id="L-14"><a name="L-14"></a> <span class="nx">Person</span><span class="p">.</span><span class="nx">call</span><span class="p">(</span><span class="k">this</span><span class="p">);</span> </span><span id="L-15"><a name="L-15"></a><span class="p">}</span> </span><span id="L-16"><a name="L-16"></a> </span><span id="L-17"><a name="L-17"></a><span class="c1">// inherit Person</span> </span><span id="L-18"><a name="L-18"></a><span class="nx">Student</span><span class="p">.</span><span class="nx">prototype</span> <span class="o">=</span> <span class="k">new</span> <span class="nx">Person</span><span class="p">();</span> </span><span id="L-19"><a name="L-19"></a> </span><span id="L-20"><a name="L-20"></a><span class="c1">// correct the constructor pointer because it points to Person</span> </span><span id="L-21"><a name="L-21"></a><span class="nx">Student</span><span class="p">.</span><span class="nx">prototype</span><span class="p">.</span><span class="nx">constructor</span> <span class="o">=</span> <span class="nx">Student</span><span class="p">;</span> </span><span id="L-22"><a name="L-22"></a> </span><span id="L-23"><a name="L-23"></a><span class="c1">// replace the sayHello method</span> </span><span id="L-24"><a name="L-24"></a><span class="nx">Student</span><span class="p">.</span><span class="nx">prototype</span><span class="p">.</span><span class="nx">sayHello</span> <span class="o">=</span> <span class="kd">function</span><span class="p">(){</span> </span><span id="L-25"><a name="L-25"></a> <span class="nx">alert</span><span class="p">(</span><span class="s1">&#39;hi, I am a student&#39;</span><span class="p">);</span> </span><span id="L-26"><a name="L-26"></a><span class="p">}</span> </span><span id="L-27"><a name="L-27"></a> </span><span id="L-28"><a name="L-28"></a><span class="c1">// add sayGoodBye method</span> </span><span id="L-29"><a name="L-29"></a><span class="nx">Student</span><span class="p">.</span><span class="nx">prototype</span><span class="p">.</span><span class="nx">sayGoodBye</span> <span class="o">=</span> <span class="kd">function</span><span class="p">(){</span> </span><span id="L-30"><a name="L-30"></a> <span class="nx">alert</span><span class="p">(</span><span class="s1">&#39;goodBye&#39;</span><span class="p">);</span> </span><span id="L-31"><a name="L-31"></a><span class="p">}</span> </span><span id="L-32"><a name="L-32"></a> </span><span id="L-33"><a name="L-33"></a><span class="kd">var</span> <span class="nx">student</span> <span class="o">=</span> <span class="k">new</span> <span class="nx">Student</span><span class="p">();</span> </span><span id="L-34"><a name="L-34"></a><span class="nx">student</span><span class="p">.</span><span class="nx">sayHello</span><span class="p">();</span> </span><span id="L-35"><a name="L-35"></a><span class="nx">student</span><span class="p">.</span><span class="nx">walk</span><span class="p">();</span> </span><span id="L-36"><a name="L-36"></a><span class="nx">student</span><span class="p">.</span><span class="nx">sayGoodBye</span><span class="p">();</span> </span><span id="L-37"><a name="L-37"></a> </span><span id="L-38"><a name="L-38"></a><span class="c1">// check inheritance</span> </span><span id="L-39"><a name="L-39"></a><span class="nx">alert</span><span class="p">(</span><span class="nx">student</span> <span class="k">instanceof</span> <span class="nx">Person</span><span class="p">);</span> <span class="c1">// true </span> </span><span id="L-40"><a name="L-40"></a><span class="nx">alert</span><span class="p">(</span><span class="nx">student</span> <span class="k">instanceof</span> <span class="nx">Student</span><span class="p">);</span> <span class="c1">// true</span> </span></pre></div> </td></tr></table>
Inheritance, Javascript, OOP