JavaScript is a versatile language with unique behaviors and types that can sometimes be confusing, especially when it comes to handling values.

I’ve covered a few concepts that often confuse as they may seem similar at first glance but represent different concepts within the language.

In this article, I’ve tried to give you all the information you’re looking for and explained the differences between declare and type in a way that will surely help you navigate JavaScript with more confidence.

So let’s get started. Stay tuned till the end.

1. Null

‘Null’ in JavaScript is a special value that indicates the intentional absence of an abstract value. It is a way for the programmer to explicitly indicate that a variable should have no value.

‘Null’ is one of the default types in JavaScript. The value ‘null’ is used to make something intentionally empty, the absence of a value. When ‘null’ is used, it means that the variable is declared to have the value ‘null’.

Attributes of ‘null’:

Type: ‘null’ is of  ‘object’ type. This may be a surprise but it is evidence of a historical bug in JavaScript.

Usage: It is commonly used to indicate that a char or jQuery should have no value.

Comparison: ‘null’ is equal to (‘==’) defined but ‘null’ is not equal to (‘===’). This means that ‘null ’ == ‘ is undefined’ is  ‘true’ but ‘null ’ === ‘ is undefined’ true.

Example:

let user = null; // The variable 'user' is explicitly set to have no value

2. Undefined

One of the default types of JavaScript is ‘undefined’. A variable is ‘undefined’ when the variable has been declared but no value has been assigned.

This does not mean that the variable is not in the assertion. It means that the variable exists because it has been created but it does not have a value.

Characteristics of ‘undefined’:

Type: ‘undefined’ is its own type

Usage: Automatically assigned by JavaScript to uninitialized variables and missing function return values

Comparison: As mentioned ‘undefined’ is similar to ‘null’ but is not strictly normal

Example:

let age; // The variable 'age' is declared but not initialized, so its value is 'undefined'

3. Undeclared

Before we know the meaning of ‘undeclare’, let us first see what it means to declare and initialize a variable

When we declare and initialize a variable we are creating a variable and storing something inside the variable

An ‘undeclared’ variable is a variable that has not been declared in the current scope. Trying to use a declared variable produces a ‘Reference Error’

Attributes of an undeclared variable:

Type: Not applicable because the variable does not exist

Usage: This usually happens when you try to access a variable that is not declared anywhere in the code

Error Handling: Accessing an ‘undeclared’ variable will result in a reference error

Example:

console.log(salary); // ReferenceError: salary is not defined

Conclusion

In short, ‘null’, ‘undefined’, and ‘undeclared’ are fundamental concepts in JavaScript that help in understanding variables and managing the human state.

For example, ‘null’ represents the intentional absence of a value implicit represents the lack of a defined/initialized variable, and implicit relates to variables that do not exist in the current scope.

Mastering these concepts will enhance your ability to debug and write cleaner, more efficient JavaScript code. Hope you found this article very important.

Stay tuned. We will keep bringing you similar articles in which you will get more and more information.

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