Example

  fetch("be.php", {
        headers: {
          'Accept': 'application/json',
          'Content-Type': 'application/json'
        },
        method: "POST",
        body: JSON.stringify({req:"put",url})
      }
    )
    .then(response => {
      if( response.ok ) {
        console.log("ok")
        window.location.reload()
      }
      return response.text()
    }).then(text=> {
      console.log(text)
    })