<a [routerLink]="['/dashboard/micebot/?a=serv11111121']">/micebot</a>
key=value
.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');
}