Prefill a form checkbox from previous page url

I am using the following code to automatically have one checkbox in a list of many prefilled when a button is clicked in a product page for more information. This code is taken from a previously solved question, but it does not work for me. What am I doing wrong?

PAGE A (button)

<a href="pageB.php#myHash" id="select-checkbox1">More Information</a>

PAGE B

$(document).ready(function(){
  var hash = location.hash;  // 
  f(hash=="#myHash"){
    ("#checkbox1").prop("checked", !$("#checkbox1").prop("checked") );  
  }
});


<input type="checkbox" id="checkbox1" name="boxset" value="XXXX">

Also PAGE A is a Wordpress page which automatically reverses the href for some reason.

<a id="select-checkbox1" href="pageB.html#myHash">More Information</a>

I have tried this in two other websites with the same problem. It obviously does not like the format. I would appreciate some help with this.