function plan() { var plan = new FormData(); var transmitter = document.getElementById("plan-transmitter").value; var receiver = document.getElementById("plan-receiver").value; var start = document.getElementById("plan-start").value; var end = document.getElementById("plan-end").value; plan.append('transmitter', transmitter); plan.append('receiver', receiver); plan.append('start', start); plan.append('end', end); var xhttp = new XMLHttpRequest(); xhttp.onreadystatechange = function() { if (this.readyState == 4 && this.status == 200) { document.getElementById("created-id").innerHTML = JSON.parse(this.responseText).id; document.getElementById("created-alert").style.display = "block"; } }; xhttp.open("POST", "/api/observation/plan", true); xhttp.send(plan); }