JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="http://cdn.sencha.com/ext/gpl/4.2.0/resources/css/ext-all.css">

JavaScript

Ext.onReady(function(){
    var store = Ext.create('Ext.data.TreeStore', {
        root: {
            expanded: true,
            children: [
                { text: "detention", leaf: true },
                { text: "homework", expanded: true, children: [
                    { text: "book report", leaf: true },
                    { text: "algebra", leaf: true}
                ] },
                { text: "buy lottery tickets", leaf: true }
            ]
        }
    });
    
    var tree = Ext.create('Ext.tree.Panel', {
        title: 'Simple Tree',
        margin: 30,
        height: 200,
        selModel : {
            type : 'treemodel',
            mode : 'MULTI'
        },
        store: store,
        rootVisible: false,
        renderTo: Ext.getBody(),
        tbar : [{text:'Selection',handler:function(){
            var sel = tree.getSelectionModel().getSelection(),
                msg = [];
            for(var i=0;i<sel.length;i++){
                msg.push(sel[i].get('text'))
            }
            
            Ext.Msg.alert('Selections',msg.join(' - '));
        }}]
    });
});