Prevent Google from indexing Angular components

The problem

Our web page is multilanguage, server-side render Angular application, and creating a JavaScript file that will dynamically change content (like SPA does) will be a hard thing to do. Some of the problems:

• We need to copy existing text from JSON files that we use for translation. And we need to keep in mind to update both places when changing the content
• On language change, we need to update content to match selected language. This requires another AJAX request to get content.
• We can’t add content for all languages and just display:none it! Google will see the hidden content.
• What if, in future, we want to hide complex content with video, image, etc.? It would create a hot mess of a JavaScript file, to include that kind of content.

The solution

We need a solution for hiding content or whole components wherever we want in Angular Web application. This way we could keep using our Angular components and Angular features like before and hide contents from Google bots.

TLTR;

• Create folder for JavaScript files
• Hide folder from Google bot
• Create dummy isRobot.js file
• Add folder to angular-cli.json
• Write robot check method
• Use check method in our components

Create folder for JavaScript files

Create folder hidefrombot in /src where we will add our dummy JavaScript file that we will use to determine if the agent is a robot or not. You can add a hidefrombot folder somewhere else, but you will need to adjust angular-cli.json different also.

Hide folder from Google bot

To disallow a Google bot to see out the script we need to hide the whole folder. We can do that by adding restriction in robot.txt file:

Disallow: /hidefrombot

If we don’t have that file, create it.

Create dummy isRobot.js file

This dummy script will be used just to see if the browser agent can access it. If the browser agent can’t execute isRobot.js then the agent is a robot. This file can be empty, or add some comment, or whatever. We do not care what is in a file, we just want to know can it be executed or not.

Add folder in angular-cli.json

To make sure that our isRobot.js is present after the application is built and deployed we need to add it like an asset. We can do that by adjusting the angular-cli.json file. There we need to add our folder in the asset part. Something like this:

{
  "project": {
    "name": "hide.from.google"
  },
  "apps": [{
    "root": "src",
    "outDir": "dist",
    "assets": [
      "assets",
      "favicon.ico",
      "robots.txt",
      {
        "glob": "*.xml",
        "input": "config/sitemaps",
        "output": "./"
      },
      "denyrobots"
    ]
  }]
}

If you created your folder somewhere else, you need to adjust your angular-cli.json file.
isRobot method and how to use it in component
We should create a service for this method or add it to our existing service. The best way is to do a one-time check-in our app, and use that information through our whole app. That way, we will try to get isRobot.js file only once and our app will stay optimized.
Assume that we have a service called SeoOptimisationService in seo-optimisation.service.ts file. Create a new method checkForCrawlingRobot and try to execute our script. Our service should also contain a flag variable that will show if the agent is Google bot or not.
isNotCrawlingRobot: boolean = false;isRobot () { const contentScriptElement = this.document.createElement(‘script’); contentScriptElement.src = ‘/ hidefrombot / isRobot.js’; contentScriptElement.async = true; contentScriptElement.onload = () => {  this.isNotCrawlingRobot = true; }; this.document.head.appendChild(contentScriptElement);}
This method will add isRobot.js in our head and try to execute it. If this happens onload event will fire and there we can change our variable.
To keep our app optimized we should call this method in our app.compoment.ts file in ngAfterViewInit() life circle. This way, calling this script won’t block our app to render and we won’t get negative points from Google. Calling our service:
// check if browser agent is a crawling robotthis.seoOptimisationService.isRobot();
The last thing we need to do is to use this service in our component. Simple as that.
Just add seoOptimisationService to our component and use isNotCrawlingRobotflag in our template.
<div *ngIf=”seoOptimisationService.isNotCrawlingRobot” class=”info-content-box”><p> Our customer service is open, the store will be open again from the end of April due to the coronavirus. </p></div>
You may wonder: what if the component is rendered before we get onload event, because we do not know when will get a response from that call. Well, we do not have to worry. When variable isNotCrawlingRobot is changed in service, it will be changed also in our component and everything will be fine.
Now, we can hide whatever content or component in our Angular application using only one service! Nice, right?