Does nodejs need to be started every time?

Node.js is a very popular server-side JavaScript running environment, widely used in web development, command line tools and other fields. However, many beginners have a question when learning Node.js: Do they need to restart every time they run a Node.js application?

The answer is not necessarily. Let’s answer this question in detail below.

First, let’s take a look at the basic working principles of Node.js. When writing an application with Node.js, we usually create a JavaScript file and then run it using the node command on the command line. For example, we can create a file called app.js and then enter:

node app.js

on the command line. This command will start the Node.js running environment and let it run our application. The application will keep running until we terminate it with the Ctrl C command.

So, if we modify the app.js file, do we need to restart Node.js for the modification to take effect? The answer is not necessarily. If we modify some static configuration parameters or data and do not involve modification of program logic, then we can use some tools to complete hot updates without restarting Node.js. For example, you can use the nodemon tool to monitor file changes and automatically restart applications when files change. The specific operation method is as follows:

1. First, we need to install nodemon. Enter in the command line:

npm install -g nodemon

2. Then, in the root directory of our application, create a configuration file called nodemon.json with the following content:

{
  "watch": ["src"],
  "ext": "js json",
  "ignore": ["node_modules"],
  "execMap": {
    "js": "node --inspect=0.0.0.0:9229"
  }
}

Among them, watch The field specifies the folder to be monitored, the ext field specifies the file suffix to be monitored, the ignore field specifies the folder to be ignored, and the execMap field specifies the command to be executed. The node command is specified here, with -- The inspect parameter enables the debugging function of Node.js.

3. Finally, enter in the command line:

nodemon app.js

This command will start the nodemon tool and let it monitor our application. When we modify a file, nodemon will automatically restart the application.

However, in more cases, we modify program logic rather than configuration parameters or data. In this case, we must restart Node.js for the changes to take effect. This is because, after we start Node.js, it will compile our application into machine code and load it into memory to run. If we modify the program logic, we need to recompile and load the machine code for the new logic to take effect.

In summary, whether Node.js needs to be started every time depends on what we modify. If we modify static configuration parameters or data, we can use tools to implement hot updates; if we modify program logic, we must restart Node.js.

I hope this article can answer your questions and let you better understand the working principle of Node.js.

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