Immutable - MDN Web Docs Glossary: Definitions of Web-related terms 编辑

An immutable object is one whose content cannot be changed.
An object can be immutable for various reasons, for example:

• To improve performance (no planning for the object's future changes)
• To reduce memory use (make object references instead of cloning the whole object)
• Thread-safety (multiple threads can reference the same object without interfering with one other)

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General knowledge

• Immutable on Wikipedia