Closures - JavaScript | MDN

Traditionally (before ES6), JavaScript variables only had two kinds of scopes: function scope and global scope. Variables declared with var are either function-scoped or global-scoped, depending on whether they are decla

Scoping with let and const

Emulating private methods with closures

Languages such as Java allow you to declare methods as private, meaning that they can be called only by other methods in the same class.

Emulating private methods with closures

Languages such as Java allow you to declare methods as private, meaning that they can be called only by other methods in the same class.

Emulating private methods with closures

Languages such as Java allow you to declare methods as private, meaning that they can be called only by other methods in the same class.

Creating closures in loops: A common mistake

Prior to the introduction of the let keyword, a common problem with closures occurred when you created them inside a loop. To demonstrate, consider the following example code.

Creating closures in loops: A common mistake

Prior to the introduction of the let keyword, a common problem with closures occurred when you created them inside a loop. To demonstrate, consider the following example code.

Creating closures in loops: A common mistake

Prior to the introduction of the let keyword, a common problem with closures occurred when you created them inside a loop. To demonstrate, consider the following example code.

Inheritance and the prototype chain

As mentioned previously, each function instance manages its own scope and closure. Therefore, it is unwise to unnecessarily create functions within other functions if closures are not needed for a particular task, as it

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This page was last modified on Nov 4, 2025 by MDN contributors.

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