Load and execute external js file in node js with access to local variables

Question

Is it easy possible to do a simple include    path to file   type of command in node js     All I want to do is have access to local variables and run a script   How do people typically organize node js projects that are bigger than a simple hello world    A fully functional  dynamic website   For example I d like to have directories like    models   views      etc

User · Answer

If you are planning to load an external javascript file s functions or objects  load on this context using the following code     note the runInThisContext method    var vm   require  vm    var fs   require  fs     var data   fs readFileSync    externalfile js    const script   new vm Script data   script runInThisContext        here you can use externalfile s functions or objects as if they were instantiated here  They have been added to this context

User · Answer

Just do a require    yourfile js     Declare all the variables that you want outside access as global variables  So instead of  var a    hello  it will be  GLOBAL a  hello  or just  a    hello   This is obviously bad  You don t want to be polluting the global scope  Instead the suggest method is to export your functions variables   If you want the MVC pattern take a look at Geddy

User · Answer

You need to understand CommonJS  which is a pattern to define modules  You shouldn t abuse GLOBAL scope that s always a bad thing to do  instead you can use the  exports  token  like this      circle js  var PI   3 14     PI will not be accessible from outside this module  exports area   function  r      return PI   r   r      exports circumference   function  r      return 2   PI   r       And the client code that will use our module      client js  var circle   require    circle    console log   The area of a circle of radius 4 is                circle area 4      This code was extracted from node js documentation API   http   nodejs org docs v0 3 2 api modules html  Also  if you want to use something like Rails or Sinatra  I recommend Express  I couldn t post the URL  shame on Stack Overflow

User · Answer

Sorry for resurrection  You could use child process module to execute external js files in node js  var child process   require  child process       EXECUTE yourExternalJsFile js child process exec  node yourExternalJsFile js    error  stdout  stderr    gt        console log    stdout         console log    stderr         if  error     null            console log  exec error    error

User · Answer

If you  are writing code for Node  using Node modules as described by Ivan is without a doubt the way to go   However  if you need to load JavaScript that has already been written and isn t aware of node  the vm module is the way to go  and definitely preferable to eval    For example  here is my execfile module  which evaluates the script at path in either context or the global context   var vm   require  vm    var fs   require  fs    module exports   function path  context      var data   fs readFileSync path     vm runInNewContext data  context  path       Also note  modules loaded with require      don t have access to the global context

User · Answer

Expanding on  Shripad s and  Ivan s answer  I would recommend that you use Node js s standard module export functionality   In your file for constants  e g  constants js   you d write constants like this   const CONST1   1  module exports CONST1   CONST1   const CONST2   2  module exports CONST2   CONST2    Then in the file in which you want to use those constants  write the following code   const  CONST1   CONST2    require    constants js      If you ve never seen the const         syntax before  that s destructuring assignment

[javascript] Load and execute external js file in node.js with access to local variables?

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