[jQuery] JSON: Cascading Dropdowns?

Does anyone have an example of a two step Cascading Dropdown working
from a single JSON object?

Here's an example of my JSON. Product Size > Product Width

"productlist":[{
"size":"XL",
"details":[
{
"id":"1",
"width":"40",
"quantityleft":"4"
},
{
"id":"2",
"width":"24",
"quantityleft":"6"
},
{
"id":"3",
"width":"22",
"quantityleft":"1"
},
"size":"S",
"details":[
{
"id":"11",
"width":"40",
"quantityleft":"4"
},
{
"id":"12",
"width":"24",
"quantityleft":"6"
},
{
"id":"13",
"width":"22",
"quantityleft":"1"
}
]
}]