Hi, Let's Learn Variables in Javascript.
Variable[Variables = Data Containers]
A JavaScript variable is a named container used to store, reference, and manipulate data values in a program. Because JavaScript is dynamically typed, you do not need to specify the type of data (like text or numbers) when creating a variable; the engine determines it automatically at runtime.
Variables are identified with unique names called identifiers.
Ex : a=10 ---> a- variable , 10- value
The rules for constructing names (identifiers) are:
- Names can contain letters, digits, underscores, and dollar signs.
- Names must begin with a letter, a $ sign or an underscore (_).Numbers are not allowed as the first character in names.
- Names are case sensitive (X is different from x).
- Reserved words (JavaScript keywords) cannot be used as names.
Dynamically Typed vs Statically Typed Languages
Statically Typed Languages
- How it works: Variable data types are known and enforced before the program runs (at compile time).
- Key traits: You must declare types explicitly, and errors are caught early.
- Pros: More optimized, faster execution, fewer surprises in production.
- Examples: C, C++, Java, Rust, Go.
Dynamically Typed Languages
- How it works: Data types are assigned and checked during execution (at runtime).
- Key traits: You don't need to specify variable types, and values can change types freely.
- Pros: Faster setup, more flexible, and code is often quicker to write.
- Examples: Python, JavaScript, Ruby, PHP.
Ways to Declare Variables Modern JavaScript uses three primary keywords to create variables:
- const: Declares a block-scoped constant value that cannot be reassigned after initialization.
- let: Declares a block-scoped mutable variable that can be reassigned later.
var: Declares a function-scoped variable. This is an older legacy keyword that is mostly avoided in modern code.
Variables are labels for data values.
Variables are containers for storing data.
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