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I am a JavaScript newbie. I am used to Java, thus I am trying to map two worlds in atrociously incorrect ways.

Questions:

  1. Each Java instance runs on a JVM. What is the JVM equivalent for JavaScript?

  2. In Java, objects occupy memory and that memory is stored on the heap. Where do JavaScript objects get stored? In other words whats the JVM's heap equivalent for JavaScript?

  3. Each function call in Java adds a stack frame. Do JavaScript function calls do the same (i.e. add a stack)?
War10ck
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JavaDeveloper
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    1. The browser. 2. The implicit [heap](http://stackoverflow.com/questions/1026495/does-javascript-have-a-memory-heap). 3. Yes. And you can trigger a [stack overflow](http://www.nczonline.net/blog/2009/05/19/javascript-stack-overflow-error/); only each Javascript function is also an Object. – Elliott Frisch Mar 03 '14 at 20:56

1 Answers1

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Java and ECMAScript are not the same language and, past generalities, have different execution models. While the JLS (Java Language Specification) is very technically precise about things like "references" and the "heap", the ECMAScript specification focuses merely on behavior.

A conforming implementation of ECMAScript must provide and support all the types, values, objects, properties, functions, and program syntax and semantics (behavior) described in this specification.

ECMAScript is executed by a "JavaScript Engine". Generally there is one "environment" per browser window; that is, each window object is the global context for at most one concurrent Program execution. This effectively means that each browser window "is a separate VM".

Each mutable object is mutable, and each object is reachable (and thus guaranteed to be alive) only as long as it is strongly referenced. The implementations certainly use "heap" memory and "references", as it is a practical/required design choice; but neither the usage of a "heap" or "references" (in this sense) is discussed in the specification.

The specification discusses the stack in terms of Execution Contexts which is composed of a logic chain.

When control is transferred to ECMAScript executable code, control is entering an execution context. Active execution contexts logically form a stack ..

user2864740
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