How to debug in node.js?

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After using node.js for a few days, I feel very novel, but the debugging problem is really frustrating. , at the beginning, I lazily learned the debugging method and just looked at the exception content. However, as the complexity of the code increased, not all errors were syntax errors. It was impossible to solve the problem without debugging, so I had to search for information and learn. How to debug it.

Supervisor that does not need to restart the service every time

Students who have used PHP must know that after modifying a script file, the new content will be loaded as long as the page server is refreshed, but node .js will put it into the memory after parsing it for the first time when it references a file. The next time it is accessed, it will be retrieved directly from the memory to improve efficiency. However, this caused some trouble for our development. After modifying a certain module It can only take effect after restarting the server, and the debugging efficiency is still very low.

So there is a supervisor plug-in in node.js to help us make file changes and automatically restart the server. Supervisor is a package of node.js. It is very simple to install. Just use the npm installation command, because we It needs to be run in the console, so it needs to be installed in the global environment

npm install -g supervisor

So we can use the supervisor to start the script

supervisor index

When we do something to the file When making changes, you can see that there are three more lines in the console and the server has been restarted

Native console debugging

node.js itself supports debugging , you can add a breakpoint by adding the debugger command in front of the statement

var server=require('./server'),
    router=require('./router'),
    requestHandlers=require('./requestHandlers');debugger;var handle={};debugger;
handle['/']=handle['/start']=requestHandlers.start;debugger;
handle['/upload']=requestHandlers.upload;
handle['/show']=requestHandlers.show;debugger;
server.start(8080,router.route,handle);

Add the debug option when starting the service

node debug index.js

Enter some commands at this time You can single-step debug, monitor local variables at breakpoints, etc. Look at the command diagram. Many commands have their abbreviations

node --debug-brk=5858 test.js

npm install -g node-inspector

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