LOADPAGE - Parsing JSON Request failed, status 200 - node.js

Question

[REGISTER SHIFT/ ASSIGNMENT FORM]
Here is my form, let me describe it; it register next week working hours, I design there are 2 cases: add new and edit in the same form.
When user select an employee, if not register shift yet, we let user register for this employee, if shift is registered already, user can edit in the same form. And I think it will be better not refresh the page, every time user change employee, the form just update and let user add/edit then submit it by post method.
I searched the web, and found a recommendation for ajax/jQuery.
Any more recommendations for me? I've just learn Nodejs/Express with PostgreSQL database.
I am trying to use ajax to load mypage from post event, I call error function in ajax to see what the error is and get:
Parsing JSON Request failed. Status 200.
I'm using NodeJS Express Server, EJS view engine, body-parser, postgresql db.
pool.connect((err, client, release) => {
if (err) {
return console.error('Error acquiring client', err.stack)
}
client.query(
'SELECT * FROM "Employee"', (err, result) => {
release()
if (err) {
res.end();
return console.error('Error executing query', err.stack);
}
console.log(typeof(result));
res.type('json');
res.render("index", {emplist : result});
res.end();
})
})
My ajax function:
$.ajax({
url: "/addshift",
type: "POST",
data: JSON.stringify(employee),
dataType: "application/json",
contentType: 'application/json',
complete: function () {
console.log("go into complete !");
},
success: function (response) {
console.log(response);
console.log("go into success !");
},
error:function(x,e) {
if (x.status==0) {
alert('You are offline!!\n Please Check Your Network.');
} else if(x.status==404) {
alert('Requested URL not found.');
} else if(x.status==500) {
alert('Internel Server Error.');
} else if(e=='parsererror') {
alert('Error.\nParsing JSON Request failed. ' + x.status);
} else if(e=='timeout'){
alert('Request Time out.');
} else {
alert('Unknow Error.\n'+x.responseText);
}
}
});

Answer 1

let's see:
"I am trying to use ajax to load mypage from post event"
Ok, so I suppose you want to get a fully formed HTML page from your $post.
Then, I see:
console.log(typeof(result));
res.type('json');
res.render("index", {emplist : result});
res.end();
res.render will return HTML, this is good for your goal. BUT, you're also specifying a JSON type with res.type. This is causing the error. HTML is not JSON clearly.
Furthermore, you don't need the call to res.end(). res.render() will finish the transaction correctly on its own, res.end is for errors or unexpected conditions.
Your ajax code is ok, but if you're trying to update an html component, like a select, you need to do that manually using the response from ajax, like so:
$("#selectElem").html(response);
Furthermore, you should check your result object from the SELECT * FROM EMPLOYEE query is correctly formatted as proper JSON