var myForm = document.createElement("form");

myForm.method = "POST";
myForm.action = strURL;
myForm.target = "_blank";

var myInput = document.createElement("input");
myInput.type = "text";
myInput.name = "sim";
myInput.value = JSON.stringify(/*data to post goes here*/);
myForm.appendChild(myInput);

document.body.appendChild(myForm);
myForm.submit();
$(myForm).hide();