Get the value of a cookie

function getCookie (name) {
	let value = '; ' + document.cookie;
	let parts = value.split(`; ${name}=`);
	if (parts.length == 2) return parts.pop().split(';').shift();
}

Splitting a string by token will produce eithe, an array with one string (same value), in case token does not exist in a string, or an array with two strings , in case token is found in a string .

The first (left) element is string of what was before the token, and the second one (right) is what is string of what was after the token.

(NOTE: in case string starts with a token, first element is an empty string)

Considering that cookies are stored as follows:

"{name}={value}; {name}={value}; ..."

In order to retrieve specific cookie value, we just need to get string that is after “; {name}=” and before next “;”. Before we do any processing, we prepend the cookies string with “; “, so that every cookie name, including the first one, is enclosed with “; ” and “=”:

"; {name}={value}; {name}={value}; ..."

Now, we can first split by “; {name}=”, and if token is found in a cookie string (i.e. we have two elements), we will end up with second element being a string that begins with our cookie value. Then we pull that out from an array (i.e. pop), and repeat the same process, but now with “;” as a token, but this time pulling out the left string (i.e. shift) to get the actual token value.

Source

https://stackoverflow.com/questions/10730362/get-cookie-by-name/15724300#15724300