Add debug instructions

- update README with debug instructions
- add `debug.js` script under `/scripts`
- update `package.json` with debug scripts

Author: Rob--

README.md

@@ -44,11 +44,18 @@ You may also need to [follow these steps](https://github.com/nodejs/node-gyp#use
 When using memoryjs, the target process should match the platform architecture of the Node version running.
 For example if you want to target a 64 bit process, you should try and use a 64 bit version of Node.
 
-You also need to recompile the library and target the platform you want. Head to the memoryjs node module directory, open up a terminal and to run the compile scripts, type:
+You also need to recompile the library and target the platform you want. Head to the memoryjs node module directory, open up a terminal and to run the compile scripts, type one of the following:
 
-`npm run build32` if you want to target 32 bit processes
+```bash
+# will automatically compile based on the detected Node architecture
+npm run build
 
-`npm run build64` if you want to target 64 bit processes
+# compile to target 32 bit processes
+npm run build32
+
+# compile to target 64 bit processes
+npm run build64
+```
 
 # Node Webkit / Electron
 
@@ -581,3 +588,53 @@ setInterval(() => {
 
 Note: a loop is not required, e.g. no loop required if you want to simply wait until the first detection of the address being accessed or written to.
 
+# Debug
+
+### 1. Re-compile the project to be debugged
+
+Go to the root directory of the module and run one of the following commands:
+```bash
+# will automatically compile based on the detected Node architecture
+npm run debug
+
+# compile to target 32 bit processes
+npm run debug32
+
+# compile to target 64 bit processes
+npm run debug64
+```
+
+### 2. Change the `index.js` file to require the debug module
+
+Go to the root directory and change the line in `index.js` from:
+```javascript
+const memoryjs = require('./build/Release/memoryjs');
+```
+
+To the following:
+```javascript
+const memoryjs = require('./build/Debug/memoryjs');
+```
+
+### 3. Open the project in Visual Studio
+
+Open the `binding.sln` solution in Visual Studio, found in the `build` folder in the project's root directory.
+
+### 4. Setup Visual Studio debug configuration
+
+  1. In the toolbar, click "Project" then "Properties"
+  2. Under "Configuration Properties", click "Debugging"
+  3. Set the "Command" property to the location of your `node.exe` file (e.g. `C:\nodejs\node.exe`)
+  4. Set the "Command Arguments" property to the location of your script file (e.g. `C:\project\test.js`)
+
+### 5. Set breakpoints
+
+Explore the project files in Visual Studio (by expanding `..` and then `lib` in the Solution Explorer). Header files can be viewed by holding `Alt` and cilcking on the header file names at the top of the source code files.
+
+Breakpoints are set by clicking to the left of the line number.
+
+### 6. Run the debugger
+
+Start debugging by either pressing `F5`, by clicking "Debug" in the toolbar and then "Start Debugging" or by clicking "Local Windows Debugger".
+
+The script you've set as the command argument in step 4 will be run, and Visual Studio will pause on the breakpoints set and allow you to step through the code line by line and inspect variables.

package.json

@@ -5,10 +5,14 @@
   "main": "index.js",
   "scripts": {
     "test": "echo \"Error: no test specified\" && exit 1",
-    "install": "node ./scripts/install.js",
+    "install": "npm run build",
+    "build": "node ./scripts/install.js",
     "build32": "node-gyp clean configure build --arch=ia32",
     "build64": "node-gyp clean configure build --arch=x64",
-    "buildtest": "cd test && MSBuild.exe project.sln //p:Configuration=Release"
+    "buildtest": "cd test && MSBuild.exe project.sln //p:Configuration=Release",
+    "debug": "node ./scripts/debug.js",
+    "debug32": "node-gyp configure rebuild --debug --arch=xia32",
+    "debug64": "node-gyp configure rebuild --debug --arch=x64"
   },
   "repository": {
     "type": "git",

scripts/debug.js

@@ -0,0 +1,35 @@
+/**
+ * [npm debug script]
+ * Purpose is to automatically detect Node process architecture and run the
+ * corresponding script to build the library for debugging.
+ * Defaults to `node-gyp rebuild` if unable to detect the architecture.
+ */
+
+/* eslint-disable no-console */
+const { spawn } = require('child_process');
+
+function run(script) {
+  console.log(`Node architecture is ${process.arch}: running "${script}"`);
+
+  const program = script.split(' ')[0];
+  const args = script.split(' ').slice(1);
+
+  // inherit stdio to print colour (helpful for warnings/errors readability)
+  const child = spawn(program, args, { stdio: 'inherit' });
+
+  child.on('close', code => console.log(`Script "${script}" exited with ${code}`));
+}
+
+const buildScripts = {
+  x64: 'run debug64',
+  ia32: 'run debug32',
+};
+
+if (Object.prototype.hasOwnProperty.call(buildScripts, process.arch)) {
+  // on Windows, npm is actually `npm.cmd`
+  const npm = /^win/.test(process.platform) ? 'npm.cmd' : 'npm';
+  run(`${npm} ${buildScripts[process.arch]}`);
+} else {
+  console.log('Unfamiliar architecture detected, this library is probably not compatible with your OS.');
+  run('node-gyp --debug configure rebuild');
+}