Introduction to Javascript 2

Understanding Scope

The scope of a variable controls where it can be accessed from in the program. It can be of

• Global Scope
• Function scope
• Block scope ( if / for etc )

Variable defination

Variables can be defined with var, const and let keywords.

• var keyword is function scoped
• let and const keyword are block scoped.

this keyword

• Different from how other languages use this.
• In JS land, value of this depends on how a function is called.
• call and apply helps in setting correct this value
  • the difference is in the way the arguments are provided
  • apply takes a array of arguments whereas call takes in individual arguments.

Hoisting

• All variable declarations are hoisted on the top of their scope.
• Hence they are processed before the code gets executed.
• var is set as undefined and can be accessed before declaration.
• let and const cannot be accessed and throws a referenceError if tried.

Sources

• https://www.freecodecamp.org/news/var-let-and-const-whats-the-difference/
• https://www.educative.io/courses/complete-guide-to-modern-javascript/m2vkA419vVG
• https://www.educative.io/courses/complete-guide-to-modern-javascript/g76wvk6D9M9