Data Structure
Networking
RDBMS
Operating System
Java
MS Excel
iOS
HTML
CSS
Android
Python
C Programming
C++
C#
MongoDB
MySQL
Javascript
PHP
Physics
Chemistry
Biology
Mathematics
English
Economics
Psychology
Social Studies
Fashion Studies
Legal Studies
- Selected Reading
- UPSC IAS Exams Notes
- Developer's Best Practices
- Questions and Answers
- Effective Resume Writing
- HR Interview Questions
- Computer Glossary
- Who is Who
What is the difference between Declaring and Initializing a variable in JavaScript?
The following is stated about declaration and initialization of a variable in ECMAScript specification −
A var statement declares variables that are scoped to the running execution context’s VariableEnvironment. Var variables are created when their containing Lexical Environment is instantiated and are initialized to undefined when created. [...] A variable defined by a VariableDeclaration with an Initializer is assigned the value of its Initializer’s AssignmentExpression when the VariableDeclaration is executed, not when the variable is created.
The above defines the difference:
- All variables are initialized with the value undefined.
- Variables declarations are initialized with undefined upon the initialization of their lexical environment.
- This initialization does not work as an assignment.
Updated on: 13-Jun-2020
387 Views
Advertisements