Javascript post JSON

XMLHttpRequest類

有很多方式可以發送http請求，相比調用$.get()，使用XMLHttpRequest類有個好處是可以設置header，並可以設置發送的body。

// Javascript code
function saveAndShowArticle() {
     var xhr = new XMLHttpRequest();
     xhr.open("POST", "/rest/article", true);
     xhr.setRequestHeader("Content-type", "application/json");
     xhr.onreadystatechange = function() {
          if (xhr.readyState == 4) {
               if (xhr.status == 200) {
               // show article after get from server
                  var article = JSON.parse(xhr.responseText);
                  window.location.href = "/article/" + article.id;
                        }
                    }
                };
          // costruct a json
          var articleJson = {};
          // $("#title").val() get value from element with "title" as id
          articleJson.title = $("#title").val();
          articleJson.markDown = $("#content_markdown").val();
          articleJson.categoryName = $("#category").val();
          articleJson.tags = $("#tags").val();
          articleJson.digest = $("#digest").val();
          // send post request with json
          xhr.send(JSON.stringify(articleJson));
    }