10 JavaScript concepts that every JavaScript Programmer must know.

1. understanding Scope:

The scope is the accessibility of variables, functions, and objects in some particular part of your code during runtime. In other words, scope determines the visibility of variables and other resources in areas of your code.

  • Global Scope
  • Local Scope

2. JavaScript Closures:

A closure is the combination of a function and the lexical environment within which that function was declared.


4. Variables:

  1. Variable Initialization: This usually occurs when a variable is declared. Here the variable is assigned a memory or space by the JavaScript engine. Because of this, once a variable is declared, it takes a value of undefined even before the assignment.
  2. Variable Assignment: Variable assignment is usually the most important step when using a variable. Here the variable is assigned data which is a value using the assignment operator “=”. Values in JavaScript take one of the standard JavaScript datatypes which are:
  3. String

5. IndexOf():

6.Array slice() Method :

7.Array slice() Method :


9.replace() :

10.map() :



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