moy-dom/src/diff/diffProps.js

A flexiable Virtual DOM library for building modern web interface.

/**
 * [diffProps diff two object(props)]
 * @param  {[Object]} newTreeProps [the new props]
 * @param  {[Object]} oldTreeProps [the old props]
 * @return {[Object]}              [null for no changes, Object for changes]
 */
export default function diffProps(newTreeProps, oldTreeProps){
  const propPatches = {}

  for(let [key, value] of Object.entries(oldTreeProps)){
    if(newTreeProps[key] !== value){
      propPatches[key] = newTreeProps[key] // undefined represents remove the attribute
    }
  }

  for(let [key, value] of Object.entries(newTreeProps)){
    if(!Reflect.has(oldTreeProps, key)){
      propPatches[key] = value
    }
  }

  for(let propPatch in propPatches){
    return propPatches
  }

  return null
}