How to uncheck all Chromium checkboxes

I found this code snippet that seemed to be working, but I tried to implement it and it gave several errors, my question is just how to disable all checkboxes after loading the site.

var filter_form = document.getElementById("filter_form");
var inputs = filter_form.getElementsByTagName("input");
for(var i = 0; i < inputs.length; i++) {
    if(inputs[i].type == "checkbox") {
      /* If default is checked, but state is not checked, check it*/
      if (inputs[i].defaultChecked == true) {
        if (inputs[i].checked != true) {
          inputs[i].checked = true;
        }
      /* If defeault not checked, but state is checked, uncheck it */
      } else {
        if (inputs[i].checked == true) {
          inputs[i].checked = false;
        }
      }
    }  
}