JavaScript Learning-Execution context (execution contexts)

A. Ecstack

The execution context is a stack, and each time the function is entered, the function context is pressed into the stack and the function context is ejected from the ecstack when the function exits.

two. Global Contexts

When the program is initialized, it is pressed into the ecstacks, for example:

Ecstack = [  globalcontext];

three. Function Code

When execution enters function, Ecstack will push into a new item, noting that the new item does not contain funtion inside the function.

(function  foo (flag) {  if  (flag) {    return;  }  Foo (true);}) (false);

When Foo is executed recursively, the status of Ecstack behaves as follows:

// First activation of Foo Ecstack = [  <foo> functioncontext  globalcontext];   // recursive activation of foo Ecstack = [  <foo> functioncontext–recursively   <foo> functioncontext  Globalcontext];

Throwing an exception that is not caught will result in the exit from one or more context.

Four. Eval Code

The variables and functions that are defined by eval affect the context in which the eval is invoked, for example:

// Influence Global Contexteval (' var x = Ten '); (function  foo () {  // and here , variable ' y ' is  //  Created in the local context  // of "foo" function  eval (' var y = + ');}) ();   // Ten // "Y" is not defined

Ecstack =[Globalcontext]; //eval (' var x = Ten ');Ecstack.push ({context:evalcontext, callingcontext:globalcontext});//Eval exited contextEcstack.pop ();//foo Funciton callEcstack.push (<foo>functioncontext); //eval (' var y = x ');Ecstack.push ({context:evalcontext, Callingcontext:<foo>Functioncontext}); //return from EvalEcstack.pop ();//return from FooEcstack.pop ();

JavaScript Learning-Execution context (execution contexts)