Loading a tree's nodes from the server

var store = Ext.create('Ext.data.TreeStore', {
proxy: {
type: 'ajax',
url: 'treeData.json'
},
root: {
text: 'Countries',
expanded: true
}
});

[{
"text": "United Kindom",
"children": [{
"text": "Glasgow",
"leaf": true
}, {
"text": "Edinburgh",
"leaf": true
}, {
"text": "London",
"leaf": true
}],
"leaf": false
},
{
"text": "France",
"leaf": true
}
...
]

Ext.create('Ext.tree.Panel', {
title: 'Countries & Cities',
width: 500,
height: 300,
store: store,
rootVisible: false,
renderTo: Ext.getBody(),
style: 'margin: 50px'
});