JS (Javascript)

Synchronous single threaded lang

1. Everything in JS happens inside the execution engine.
2. This execution environment has two components:-
   1. Memory component/ variable environment
      • it stores all the variable (in form of key value) and functions.
      • it is the phase one (where the initial value for variable is undefined)
      • the value for function is the code inside the function.
   2. Code component/ Thread of execution
      • it is the place where code is executed.
      • it is single thread where code is executed one line at a time.
      • it is the second phase.
      • it replaces the value of variable the current one.
      • for function it creates a new execution context and so on if another function is present inside .
3. A Call stack is maintained where the 1st one is Global exectuion context
   • it maintains the execution order of execution context.
   • Also called as runtime stack, control stack, program stack, execution context stack, machine stack