var content = document.getElementById("content").value;
jQuery.ajax({
    type:'post',
    url:'add.php',
    data:"content=" + content, // value is '?'
    dataType : "json",
    success:function(response){
        alert('success:'+response.msg);
    },
    error: function(msg){
        alert(msg);
    }
});

data = data.replace( jsre, replace );