node. JS Learning Diary (ii) node. JS Scope

Tag: module scope chain Diary error col var exports load default

node. JS Scope

Test whether the package1 can invoke functions within Package2 through require ("./package2"):

 1  //  Paackage1.js  2  var  a1 = 1 3  4  require ("./package2" );  5  6  /*   Even if require Package2, you cannot call function double_a  */  7  a1 = double_a (A1); // double_a is not defined  8  9  console.log ("package1:" + A1); 

1 // Paackage2.js 2 function Double_a (a) {3     return A * 2; 4 }56 exports.double_a = double_a;

Error, and cannot call

Package1 the correct way to invoke a function within Package2:

 1  //  Package1  2  var  a1 = 1;  3  4  /*  todo: Gets the exports object for Package2  */ Span style= "COLOR: #008080" >5  var  Package2 = require ("./package2"  6  7  A1 = Package2.double_a (A1);  8  console.log ("Package2:" + A1); 

1 // Package2 2 function Double_a (a) {3     return A * 2; 4 }56/*TODO: Mount the double_a to the Exports object */7 exports.double_a = double_a;

function successfully called

Try another one, use the scope chain, let Package1 get the variable inside the Package2

 1  //  Package1  2  var  Package2 = require (". /package2 " 3  console.log ("Name:" + package2.getname ()); 

1 // Package2 2 var name = "Lyjn"; 3 4 /* Todo:exports Set a GetName method to get the name */ 5 function () {6     return name; 7 };

Fully OK

2. Knowledge points in node only module scope, no global scope require the main role

1.加载模块并执行模块中的代码;2.返回exports对象;

Exports object

1.所有模块都有一个exports对象，默认值是一个空对象`{}`;2.可以给exports对象添加属性;

Little Tricks

1.require js file can be shed. Js,require ("./package.js") is equivalent to require ("./package")

node. JS Learning Diary (ii) node. JS Scope