Update 42-JavaScript-Engine.md

Author: sajidhamdard

notes/English/42-JavaScript-Engine.md

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+### JavaScript Engine
+A JavaScript engine is a program that executes JavaScript code. It's responsible for compiling JavaScript code into machine code, optimizing the code for performance, and executing it. Some popular JavaScript engines include:
+
+1. V8: Developed by Google and used in Google Chrome and Node.js.
+2. SpiderMonkey: Developed by Mozilla and used in Firefox.
+3. JavaScriptCore: Developed by Apple and used in Safari and some other Apple products.
+4. Chakra: Developed by Microsoft and used in Microsoft Edge and Internet Explorer.
+5. Nashorn: A newer engine developed by Oracle for use with the Java Virtual Machine (JVM).