How Can I Unset JavaScript Variables?

Unsetting JavaScript Variables

A JavaScript variable can be removed from a scope using the delete operator, which removes a property from an object. However, this operator is not applicable to variables created with the var keyword, raising the question of how to unset such global variables.

Unsetting Variables Declared with var

Variables declared with var cannot be deleted using the delete operator. They are stored in the variable environment of the scope where they are declared and cannot be removed unless the scope is destroyed.

Therefore, unsetting variables declared with var is not recommended.

Unsetting Variables Declared Without var

Variables declared without the var keyword, known as global variables, are properties of the window object. To unset such variables, the delete operator can be used:

delete window.variableName;

However, it's important to note that this will also remove the property from the global object, which may have unintended consequences.

Notes:

• Hoisted variables declared with var will still be accessible in the variable environment, even if they are assigned later in the code.
• Using strict mode changes the lookup rules for variables. Variables declared without var will raise an "undeclared variable" error.

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