JS Code Execution process

A: First-blood: The first step of any program execution will always first check that there are no syntax errors, if any, then directly throw a syntax error, jump directly,

Two: Second-blood: precompiled , precompiled there will be four execution procedures,1: Create the execution period context (AO objects ====activation object),2: Add attributes (parameters and declared variables) to the AO object, and its value is Undefind,3: uniform argument value and formal parameter,4: find function declaration (not including expression assignment var a=function () {}), and assign value,5 , executes the function itself.?, the GA object is created in the global, there is no third step, Ga=window

JS Code Execution process