Here are some question-based titles that fit the content of your JavaScript article: * **JavaScript: Null vs. Undefined: What\'s the Difference and How to Check?** * **JavaScript Equality: When Shoul

JavaScript: Comparing Null vs. Undefined and Understanding the Difference Between == and ===

Checking for Null and Undefined

In JavaScript, you can check if a variable is null or undefined using the following methods:

• For null:

  • if (a === null) or
  • if (a == null) (Note: Also evaluates to true for undefined)

• For undefined:

  • if (typeof a === "undefined") or
  • if (a === undefined) or
  • if (a == undefined) (Note: Also evaluates to true for null)

Difference Between Null and Undefined

• Undefined: A generic value representing the absence of a value or property. It is the default value for uninitialized variables or missing function arguments.

• Null: A special value indicating an intentional absence of an object reference. It is used in situations like:

  • When a DOM element is not found.
  • When an object property does not exist.

Difference Between == and ===

The main difference between == and === is type coercion.

• == (Abstract Equality Comparison):

  • Performs type coercion to attempt to match the operands.
  • For example, 1 and "1" are considered equal (true) because they are coerced to the same number type.

• === (Strict Equality Comparison):

  • Checks for equality without any type coercion.
  • 1 and "1" are considered not equal (false) because they are different types.

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