export function warn (message) { if (process.env.NODE_ENV !== 'production') { console.error(message) } } export function deprecated (fn, message) { if (process.env.NODE_ENV === 'production') return fn let warned = false const newFn = function (...args) { if (!warned) { warned = true console.error(message) } return fn.apply(this, args) } // copy all properties Object.assign(newFn, fn) return newFn }