Decorates Mithril hyperscript function with a logger which assigns a persistent numeric id to nodes and logs their lifecycles. Useful for debugging Mithril rendering sequence.

m.spy.mjs

// imort m from 'mithril'

export default Object.assign(
  decorate(m), 
  
  m, 
  
  {
    fragment: decorate(m.fragment),
  },
)

const nodes = new WeakMap
let   count = 0

function decorate(visitor){
  return function(){
    const node = visitor.apply(this, arguments)
    
    if(!node.attrs)
      node.attrs = {}

    void
      'oninit view oncreate onbeforeupdate onupdate onbeforeremove onremove'
        .split(' ')
        .forEach(key => {
          const method = node.attrs[key]
          
          node.attrs[key] = function(){
            const id = xet(nodes, this, () => count++)
            
            console.log(id, key, node)
            
            if(method) 
              return method.apply(this, arguments)
          }
        })
    
    return node
  }
}