Title here
Summary here
Debugging
Definition
Debugging involves examining and testing software to understand its behavior, identify any anomalies or errors.
Node.js
VSCode
Getting started
You can attach VSCode to a Node.js process in only two steps. See docs.
- Launch the process in debug mode:
- Run and attach:
node --inspect index.js - Wait for the debugger to attach before running:
node --inspect-brk index.js
- Attach VSCode to the process:
Press CTRL+Shift+P to open a Quick Pick menu, then select Debug: Attach to Node Process.
Choose the process you want to debug. Then, the Run and Debug window will appears:
Restart frame
The Node debugger supports restarting execution at a stack frame. See docs.
Tutorial - GIF
Conditional breakpoint
Conditional breakpoints are breakpoints that only pause when an expression returns a truthy value. See docs.
Tutorial - GIF
Logpoints
Log a message or value when code hits a certain location. See docs.
Tutorial - GIF
The arguments object
arguments is an array-like object accessible inside functions that contains the values of the arguments passed to that function.
Demo - Custom debug function
function _debugFunc(args) {
let funcName = (new Error()).stack.match(/at (\S+)/g)[1].slice(3); // handle strict mode
console.log(`\n===> call ${funcName}(args.length = ${args.length})`);
Array.from(args).forEach((arg, index) => {
if (typeof arg === "string" && arg.length > 20) {
console.log(` | args[${index}] = (${typeof arg}) ${arg.substring(0, 20) + "..."}`);
} else if (typeof arg == "function") {
console.log(` | args[${index}] = (${typeof arg}) ${arg.toString().substring(0, 20) + "..."}`);
} else if (typeof arg == "object") {
console.log(` | args[${index}] = (${typeof arg})`);
console.log(arg);
} else {
console.log(` | args[${index}] = (${typeof arg}) ${arg}`);
}
});
}
function sum(a, b) {
_debugFunc(arguments);
return a + b;
}
function sayHello(name) {
"use strict";
_debugFunc(arguments);
console.log(`Hello ${name} !`);
}
function multiply(obj) {
_debugFunc(arguments);
return obj.first * obj.second;
}
console.log(sum(3, 5));
sayHello("world");
console.log(multiply({first: 12, second: 2}));$ node example.js
===> call sum(args.length = 2)
| args[0] = (number) 3
| args[1] = (number) 5
8
===> call sayHello(args.length = 1)
| args[0] = (string) world
Hello world !
===> call multiply(args.length = 1)
| args[0] = (object)
{ first: 12, second: 2 }
24