Video – JavaScript object instances does not copy definition from the class

I recently wrote a blog post about Two Problems of a JavaScript Class. In my opinion one gotchas in a JavaScript class is , object instances does not copy definition from the class.

Watch this video to understand it through codes.  f you like the video , do not forget to subscribe to our YouTube Channel for notification about future video tutorials.


What is “let” statement in JavaScript?

Using the let statement, you can create Block scoped local variables in JavaScript. The let statement was introduced in the ECMAScript 6 standard of JavaScript.

Before ECMAScript 6, JavaScript had three types of scoping:

  • Global scoping
  • Functional scoping
  • Lexical scoping

To explore let statement in detail, consider the code snippet given below:

You will get this output for the above code listing:


In the above listing, variable x is declared using the var statement. Hence, the scope of variable x is a function scope. Variable x inside the if statemnet is same variable x which was created outside the if statement. So, when you modify the value of variable x inside the if statement block, it modifies the value for all references of variable x in the function.

To avoid this, you need block-level scoping, and the let statement allows you to create a block-scoped local variable.

Let’s modify the above code snippet and use the let statement to declare the variable:

In the above code snippet, you are declaring scope level local variable x using the let statement. Therefore updating value of variable x inside the if statement will not affect value of variable x outside the if statement.

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