JS concat not empy object values

concat.js

const myObj = { 
	a: 1,
  b:'foo',
  c: '',
  d: null,
  e: undefined
  };

const removeEmpty = (obj) => {
  Object.keys(obj).forEach((key) =>{
    if (obj[key] === undefined || obj[key] === '' || obj[key] === null) {
      delete obj[key];
    } else {
      obj[key] = key + '=' + obj[key];
    }
  });
  return obj;
};

let aux_str = Object.values(removeEmpty(myObj)).join('&');

console.log('asdf'.concat('&',aux_str));

const removeEmpty = (obj) => {
  Object.entries(obj).forEach(([key, val]) => {
    if (obj[key] === undefined || obj[key] === '' || obj[key] === null) delete obj[key]
    else obj[key] = key + '=' + delete obj[key]
     })
}
console.log(removeEmpty(myObj));