title: why should we add this while calling a method in react
body: <p>I  am having a class based component in react,the following is a piece of code 
  which uses es7 syntax so that i can access my variables of my class without binding this      </p>
  
  <pre><code>inputChangedHandler = (event, inputIdentifier) =&gt; {
          console.log(we are inside the inputhandler)
         };
  </code></pre>
  
  <p>According to my knowledge inputChangeHandler in a method from es7 syntax </p>
  
  <pre><code>  &lt;Input
  changed={this.onChangedHandler}/&gt;
  /&gt; 
  </code></pre>
  
  <p>In these lines i am passing my  inputChangeHandler as props to my component </p>
  
  <p>Following things i tried to search but i didn't find any help please help me </p>
  
  <p>1) According to my knowledge  we never used this for calling a method inside a class but why did we even use this for calling onChangeInputHandler</p>
  
  <p>2) Where  are  we assigning memory to the methods which we create in react </p>
  
  <pre><code>  class A {
  
      b (){
          console.log("we are inside the b method")
      }
  }
  
  var a = new A()
  a.b()
  we are inside the b method
  </code></pre>
  
  <p>Following is my javascript code which i created a method inside class and accessed it without this</p>