how to replace a hard coded value with a variable?

Question

I want to replace the hard coded string "Categories" with a variable. How can I do that? Instead of having Categories all the time, the word Categories may be replaced by the value held by a variable id, var id.

$(this).closest('ul').append('<li><input type="hidden" name="Categories.Index" value=' + newValue + ' /><input type="text" value=""  name="Categories[' + newValue + '].Name" style="width:280px"/><input type="hidden" value=""  name="Categories[' + newValue + '].ID" style="width:280px"/><input type="button"  value= "Add" /> </li>');

Answer 1

Just concat it the same way you already do with newValue:

name="' + id + '[' + newValue + '].ID"

Do the same for every occurence of Categories.

Answer 2

var id = 'Categories';
$(this).closest('ul').append('<li><input type="hidden" name="' + id + '.Index" value=' + newValue + ' /><input type="text" value=""  name="' + id + '[' + newValue + '].Name" style="width:280px"/><input type="hidden" value=""  name="' + id + '[' + newValue + '].ID" style="width:280px"/><input type="button"  value= "Add" /> </li>');

Answer 3

This finds every element with a name starting with "Categories" and replaces it with the variable id.

var id = "something";
var el = $("[name^=Categories]");
el.attr("name", id + el.attr("name").substr("Categories".length));

The result with your above example is an input with name="something.Index"