Every browser has a JavaScript engine that executes JavaScript code and converts it into machine code. Let’s break down the process step-by-step:
1. Parsing the Code
When JavaScript code is executed, the Parser reads the code and produces an Abstract Syntax Tree (AST), which is stored in memory. The AST represents the structure of the code in a tree format.
2. Interpreting the Code
The Interpreter processes the AST and generates bytecode or machine code. This code is then executed by the computer. The interpreter ensures that the code runs efficiently by converting it into a form that the machine can understand.
3. Profiling the Code
The Profiler is a component of the JavaScript engine that monitors the execution of the code. It collects data on how the code is running, which helps in optimizing performance.
4. Just-In-Time (JIT) Compilation
The Optimizing Compiler, also known as the Just-In-Time (JIT) Compiler, uses profiling data to make certain assumptions and produce highly optimized machine code. This process helps in improving the performance of the code by compiling it just before execution.
5. Managing the Call Stack and Memory Heap
During execution, the Call Stack keeps track of the currently executing functions, while the Memory Heap is used for memory allocation. The call stack ensures that functions are executed in the correct order, and the memory heap manages the allocation of memory for variables and objects.
6. Garbage Collection
Finally, the Garbage Collector comes into play to manage memory by reclaiming memory from unused objects. This process helps in preventing memory leaks and ensuring efficient use of memory.
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