How do I pass a URL as a parameter? [closed]

Container is a string and you are treating it as a jQuery object. That is your problem.

var container =  document.getElementById(id).value;  //String here    
var ddscore = container.closest('#field1').val();    //Act like it is jQuery here

and farther down in the code

writeLinkScore(id,field1, field2);  //where is field1 and field2 defined?

And you are not passing a string, you are passing in an object

<button onclick="showInput(link)">Click me</button>

---

<button onclick="showInput('link')">Click me</button>

and

function showInput(id) {
    var field1 = $('#field1').val();
    var field2 = $('#field2').val();
    writeLinkScore(id, field1, field2);  
}