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Dload

Hot reload plugin for node.js

Useage

npm install dload

require & reload

API: dload.reload(full_path_of_target_module)

There are three files (m1.js,m2.js,m3.js), and both of m2.js and m3.js depend on m1.js,the code below will show how to do hot-reload:

The content of m1.js:

exports.name="abc";

m2.js:

const dload = require("dload");
const mo = dload.new();


mo.m1 = require("./m1.js");//just require m1.js


exports.func=function(){
  return mo.m1.name;
}

m3.js:

const dload = require("dload");
const mo = dload.new();

mo.fs = require("fs");
mo.co = require("zco");//npm install zco
mo.path = require("path");//npm install path
mo.m2 = require("./m2.js");// require m2.js
mo.m1 = require("./m1.js"); // require m1.js

const m1_content='exports.name="abc";';

mo.co(function*(co_next){

    let data = mo.m2.func();

    console.log(data);//output "abc"

    /**
       let's modify the content of m1.js  and reload it .
    */
    let new_content = m1_content.replace(/abc/,"hello world");//replace `abc` to `hello world`

    yield mo.fs.writeFile("./m1.js",new_content,co_next);//rewrite file `m1.js`

    dload.reload(mo.path.join(__dirname,"./m1.js"));//reload file `m1.js`

    data = mo.m2.func();

    console.log(data);//output  "hello world"

    console.log(mo.m1.name);// output "hello world"

})()

Just run m3.js.

Output:

abc
hello world
hello world

From the outputs ,we will see that the module m1 is be updated globally, and all we need to do is just run dload.reload(target_module).

_release

Some modules need to release resource manually when reload. you can define a method named _release for the module to achieve this.

example:

const  handler = setInterval(function(){
   //... do something
},1000)

//exports.xxx= xxx;
//exports.xxx= xxx;
//exports.xxx= xxx;

//dload will run this method before reload
exports._release = function(){
   if(handler){
     clearInterval(handler);
   }
}

Reload_one_file

dload.reload will delete the old module recursively ,so the child modules (the module tree built by node.js's require system) will be deleted at the same time.But in most cases ,only a few files are changed ,we just want to reload a single file. Now, you can use dload.reload_one_file to achieve this.

API: dload.reload_one_file(full_path_of_target_module)

How does it work

The mo in the example code is returned by dload.new(), at first ,mo is an empty object.What's important is 'mo' is also hold by dload. When module is been reloaded ,dload just assign the new module to mo, this operation will update target module globally.Because the reference of old module only exist in module system and mo,and they are all under control,so there is no problem with memory management.

Warning

Don't do operation like this:

const m3 = mo.m3;
//******

This operation will make target module out of dload's control.