README.md

It appears that:

• virtual-hyperscript is creating a new EvHook on each call
• the diffing algorithm compares the Hooks with reference equality, not the value inside the hook, so they are different every time
• the result is that all ev-* handlers are patched on every diff

The file explicit.js shows the behaviour I expected, no patch needed. The file hyperscript.js demonstrates the issue, which is this patch:

VirtualPatch {
     type: 4,
     vNode: 
      VirtualNode {
        tagName: 'DIV',
        properties: [Object],
        children: [Object],
        key: undefined,
        namespace: null,
        count: 1,
        hasWidgets: false,
        hasThunks: false,
        hooks: [Object],
        descendantHooks: false },
     patch: { 'ev-click': [Object] } }

explicit.js

//
// This code works as expected
//
const {VNode, VText, diff, create} = require('virtual-dom');
const Delegator = require('dom-delegator');
const EvHook = require('virtual-dom/virtual-hyperscript/hooks/ev-hook');

const onClick = ev => (
    console.log('clicked', ev.target)
);

const delegator = Delegator();
delegator.listenTo('click');

const hook = new EvHook(onClick);

// here I explicitly create the vdom, and use the same EvHook every time
const render = () => (
    new VNode('DIV', {'ev-click': hook }, [ new VText('text') ])
);

const tree = render();
const tree2 = render();
const p = diff(tree,tree2);
console.log(p);
/* output:
{ a: 
   VirtualNode {
     tagName: 'DIV',
     properties: { 'ev-click': [Object] },
     children: [ [Object] ],
     key: undefined,
     namespace: null,
     count: 1,
     hasWidgets: false,
     hasThunks: false,
     hooks: { 'ev-click': [Object] },
     descendantHooks: false } }
*/

hyperscript.js

//
// This code demonstrates the issue
//
const {h, diff} = require('virtual-dom');
const Delegator = require('dom-delegator');

const onClick = ev => (
    console.log('clicked', ev.target)
);

const delegator = Delegator({defaultEvents: false});
delegator.listenTo('click');

// here I use virtual hyperscript, and use the same function every time
const render = () => h('div', {'ev-click': onClick }, ['text']);

const tree = render();
const tree2 = render();
const p = diff(tree,tree2);
console.log(p);

/* output:
{ '0': 
   VirtualPatch {
     type: 4,
     vNode: 
      VirtualNode {
        tagName: 'DIV',
        properties: [Object],
        children: [Object],
        key: undefined,
        namespace: null,
        count: 1,
        hasWidgets: false,
        hasThunks: false,
        hooks: [Object],
        descendantHooks: false },
     patch: { 'ev-click': [Object] } },
  a: 
   VirtualNode {
     tagName: 'DIV',
     properties: { 'ev-click': [Object] },
     children: [ [Object] ],
     key: undefined,
     namespace: null,
     count: 1,
     hasWidgets: false,
     hasThunks: false,
     hooks: { 'ev-click': [Object] },
     descendantHooks: false } }

*/