How to check for existing meta tag before generating a new one with javascript (or jquery)?

I'm developing a widget that creates basic SEO tags that could already exist on a page so I'm wanting to make sure the widget checks for existing tags before the new tag is generated.

For example, one of the tags that the widget produces is

<meta name="description" content="Description of the webpage"/>

Since this tag is one that most pages already have, is there a way to use javascript to check for the tag before writing it?

Solution

Here is the plain Javascript solution (no libraries):

Check for the meta description element using: document.querySelector("meta[name=description]");

If found, access its content attribute using .getAttribute("content").

Demo:

if(document.querySelector("meta[name=description]")){

  if(document.querySelector("meta[name=description]").getAttribute("content") === "Description of the webpage")

    console.log("meta description with content 'Description of the webpage' found");
    // do something

}
else{

  console.log("meta description not found");
  // do something

}

<meta name="description" content="Description of the webpage"/>

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