How to parse URL correctly?

Question

JavaScript

We have a link -->

<a [routerLink]="['/dashboard/micebot/?a=serv11111121']">/micebot</a>

In general, the essence is that you need to check the url, whether there is an "a" after the question mark and whether it is equal to "a".
12 characters in which small Latin letters and numbers from 1 to 5.
If not, then redirect

Answer 1

if("<a [routerLink]=\"['/dashboard/micebot/?a=serv11111121']\">/micebot</a>".search(/\?a=[a-z1-5]{12}[^a-z1-5]/) == -1){
  window.location ="redirect url";
}

Answer 2

It's better to separate the part with the parameters, and then break it into parts like key=value.
It will be a universal solution.
It would be easier to do exactly what you asked: check for "a" immediately after the question mark:

var text = `<a [routerLink]="['/dashboard/micebot/?a=serv11111121']">/micebot</a>`;
var m = text.match(/\?a=([a-z1-5]*)/);
if (m) {
  let a = m[1];
  console.log('"a" существует и равно ', a);
  if (a.length == 12) console.log('Длина "a" ровно 12, не больше');
}