Express is unable to obtain the data from the front desk via jquery post.

  node.js, question

The code of the front end

Var a = '{\"data\":{\"name\ ":"Zhang San ","age \ ":25}}';
 $.ajax({
 type: "post",
 url: "/new",
 dataType: "json",
 data: a,
 success: function (data) {
 alert("success");
 },
 error: function (err) {
 Alert("error: "plus err");
 bracket
 });

The back-end code

router.post('/', function (req, res) {
 var a = req.body;
 console.log(a.data.name);
 });

The project was built with express. Therefore, there is a requirement (“body-parser”)

But when I wanted to get the name in the data from the front desk, I couldn’t. Direct error reporting. What is the problem?

Var a = {"data":{"name ":"Zhang San ","age":25}};