Pass value in POST Method using JavaScript

This is my JavaScript function: I get this function by google it.

function postURL() {
    var jobValue = document.getElementsByName('folderName')[0].value;
    url = 'http://localhost:8888/TaaS/Sachin/Input' + "?FolderName=" + jobValue;
    var form = document.createElement("FORM");
    form.method = "POST";
    //if(multipart) {
    form.enctype = "multipart/form-data";
    //}
    form.style.display = "none";
    document.body.appendChild(form);
    form.action = url.replace(/\?(.*)/, function(_, urlArgs) {
        urlArgs.replace(/\+/g, " ").replace(/([^&=]+)=([^&=]*)/g, function(input, key, value) {
            input = document.createElement("INPUT");
            input.type = "hidden";
            input.name = decodeURIComponent(key);
            input.value = decodeURIComponent(value);
            form.appendChild(input);
        });
        return "";
    });
    form.submit();
}

I call this function during onclick;

<button type="submit" class="btn btn-primary start" onclick="postURL()">
    <i class="glyphicon glyphicon-upload"></i>
    <span>Create Folder</span>
</button>

I am using node.js in my server side. During the button click event in server side, the POST method is calling, but I don't know how to retrieve the "jobValue" in node.js file during POST method.

POST Method:

function(req, res) {
    switch (req.method) {
        case 'OPTIONS':
            res.end();
            break;
        case 'POST':
            console.log('req.url: ' + req.url);
            break;
        default:
            res.statusCode = 405;
            res.end();
    }
}

How to get that value in node.js file?

You didn't specify but I'm going to assume you're using Express on the server side. Despite POSTing a form, you're sending the jobValue as a query string parameter (FolderName) in the example so you'd get it in the handler function with:

req.query.FolderName

In the context of your callback:

function(req, res) {
    switch (req.method) {
        case 'OPTIONS':
            res.end();
            break;
        case 'POST':
            var jobValue = req.query.FolderName;  //<-- Your variable
            console.log('req.url: ' + req.url);
            break;
        default:
            res.statusCode = 405;
            res.end();
    }
}