Mutable

A mutable value is one that can be changed without creating an entirely new value, in comparison with {{Glossary("immutable", "immutable values")}}.

In {{glossary("JavaScript")}}, {{Glossary("Object","objects")}} and {{Glossary("Array","arrays")}} are mutable by default — their properties and elements can be changed without creating a new object or array. By contrast, {{Glossary("primitive", "primitive values")}} are immutable — once a primitive value is created, it cannot be changed, although the variable that holds it may be reassigned another value.

See also

• Immutable object on Wikipedia
• Related glossary terms:
  • {{glossary("Immutable")}}