Javascript post JSON

XMLHttpRequest类

有很多方式可以发送http请求，相比调用$.get()，使用XMLHttpRequest类有个好处是可以设置header，并可以设置发送的body。

// Javascript codefunction 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));    }