Thanks to this tip on StackOverflow, here is how you add Bootstrap IntelliSense to your Visual Studio Code project.   It’s a bit tedious, so hopefully there will be a Bootstrap extension in the future that will automate all of this.

  1. Install the HTML CSS Support Extension as an extension to VS Code.
  2. Add Bootstrap to your project.  If you’re using Node Package Manager (NPM):
    npm install bootstrap@3
  3. Go to File -> Preferences -> Settings in VS Code and select Workspace from the USER SETTINGS dropdown on the right.  Add and save the following code:
    {
     "editor.quickSuggestions": {
     "comments": false, // <- no 24x7 IntelliSense in comments
     "strings": true, // but in strings and the other parts of source files
     "other": true
     }
    }
    
  4. Inside your project’s .vscode folder, create a new file called resources.json.  Add the following code to that file:
    {
        "css": {
            "style": [
                "node_modules/bootstrap/dist/css/bootstrap.css"
            ]
        }
    }
  5. Restart VS Code and enjoy the IntelliSense goodness!