What does writing to arguments[0] do to the parameter in each of these functions?

function sloppy(a) {
  arguments[0] = 99;
  return a;
}
 
function strict(a) {
  "use strict";
  arguments[0] = 99;
  return a;
}
 
function withDefault(a = 0) {
  arguments[0] = 99;
  return a;
}
 
function missing(a) {
  arguments[0] = 99;
  return a;
}
 
console.log(sloppy(1), strict(1), withDefault(1), missing());