JavaScript - Getting HTML form values

HTML:

<input type="text" name="name" id="uniqueID" value="value" />

JS:

var nameValue = document.getElementById("uniqueID").value;

If you want to retrieve the form values (such as those that would be sent using an HTTP POST) you can use:

JavaScript

const formData = new FormData(document.querySelector('form'))
for (var pair of formData.entries()) {
  // console.log(pair[0] + ': ' + pair[1]);
}

form-serialize (https://code.google.com/archive/p/form-serialize/)

serialize(document.forms[0]);

jQuery

$("form").serializeArray()

Here is an example from W3Schools:

function myFunction() {
    var elements = document.getElementById("myForm").elements;
    var obj ={};
    for(var i = 0 ; i < elements.length ; i++){
        var item = elements.item(i);
        obj[item.name] = item.value;
    }

    document.getElementById("demo").innerHTML = JSON.stringify(obj);
}

The demo can be found here.