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_posts/2024-05-11-js-intermediate-13-nodejs-debugging-cli.md

@@ -1,13 +1,90 @@
 ---
-title: Javascript Intermediate 0
+title: Javascript Intermediate 13 - Nodejs debugging on the CLI 
 tags: javascript, programming, coding, nodejs, syntax
 article_header:
   type: cover
   image:
     src: images/js-intermediate-dog-02.png
 ---
 
-# Title
+
+There may be thousands of libraries and utilities that allow you debug **nodejs** projects, but I am going to write few lines on how to do it using the node built-in tool.
+Is not nearly as powerful as **gdb** , but using the right strategy to approach the process can clarifying as well as timesaving, as you wont be needing to install some other additional tools.
+
+
+You can start debugging your proyect via the entry file by
+```
+node inspect <myfile.js>
+help
+```
+
+You get the commands over there but mainly we will be focusing on the state of the variables as the code statements are been executed.
+
+
+First set a breakpoint, someline on your code so you can iterate from there
+
+```
+# set breakpoint
+sb(<lineNum>)
+```
+
+Then you want to basically use one of these three commands
+
+```
+next, n               Continue to next line in current file
+step, s               Step into, potentially entering a function
+cont, c               Resume execution
+```
+
+Continue to iterate to the next time you get to the following break point
+Next and step if you want to execute one line at a time.
+Note that step implies check further into function calls. 
+If using Step within buil-in functions and libraries, it will take you to lines of code outside the codebase of the project. 
+Just bear that in mind as it may confuse you.
+
+At any prompt point on the debugger (when it is paused) , you can issue commands such as.
+
+```
+#exec('<codeToExecute>'
+exec('console.log(i)')
+```
+
+But what you really want to do, is to watch variables. They will get printed out at each Step.
+
+```
+watch('<varName>')
+```
+
+Normaly you want to watch the state many variables at the same time, for that you would need like various watch commands. 
+What I personally use (because I am going to be repeating the same steps backs and forths) is to write a one-liner to activate such as watch command. 
+So at the end of my .js file  I write something like
+
+```
+/*
+sb(20)
+watch('varA');watch('varB');watch('varC');watch('varD');watch('varE');
+*/
+```
+
+So I remember, the commands I have to do and just focus on reading the output of the debugger instead.
+
+Personally it is a shame that you cannot set a breakpoint somewhere on your code in a deterministic way.
+Say you want to target a function entry point (a function call) you check the lineNumber where that happens and do `sb(23)` , but say you modify some lines previous that line , then that `sb(23)` is no longer pointing to the same statement.
+
+If you can and want modify the codeIn node.js you have the following statement which will tell the debugger to create a breakpoint there
+```
+debugger;                       // DEBUGGER BREAKPOINT
+```
+
+But if not , note that breakpoint lineNo
+
+
+Finally to exit the debugger
+
+```
+.exit
+```
+
 
 ## Javascript Intermediate tutorials