Meituan-Dianping/mpvue · error

data functions should return an object: https://vuejs.org/v2

Error message

data functions should return an object:
https://vuejs.org/v2/guide/components.html#data-Must-Be-a-Function

What it means

Raised in initData when the resolved data value is not a plain object: either the data option was a function whose return value was a primitive/array, getData caught an exception and returned {}, or a non-function data was set to a non-object. Vue replaces data with an empty object after warning, so the component renders with no reactive data properties — usually followed by 'Property or method is not defined' errors in the template.

Source

Thrown at src/core/instance/state.js:123

    }
    // static props are already proxied on the component's prototype
    // during Vue.extend(). We only need to proxy props defined at
    // instantiation here.
    if (!(key in vm)) {
      proxy(vm, `_props`, key)
    }
  }
  observerState.shouldConvert = true
}

function initData (vm: Component) {
  let data = vm.$options.data
  data = vm._data = typeof data === 'function'
    ? getData(data, vm)
    : data || {}
  if (!isPlainObject(data)) {
    data = {}
    process.env.NODE_ENV !== 'production' && warn(
      'data functions should return an object:\n' +
      'https://vuejs.org/v2/guide/components.html#data-Must-Be-a-Function',
      vm
    )
  }
  // proxy data on instance
  const keys = Object.keys(data)
  const props = vm.$options.props
  const methods = vm.$options.methods
  let i = keys.length
  while (i--) {
    const key = keys[i]
    if (process.env.NODE_ENV !== 'production') {
      if (methods && hasOwn(methods, key)) {
        warn(
          `method "${key}" has already been defined as a data property.`,
          vm
        )

View on GitHub (pinned to 6c5d78ee04)

Solutions

1. Make the data option a function that returns a plain object: data() { return { count: 0 } }
2. Check the function's return statement — it must return an object literal, not a primitive, array, or undefined
3. If data() throws, fix the exception (e.g. accessing undefined nested props inside data)

When it happens

Trigger: Thrown at src/core/instance/state.js:123 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of Meituan-Dianping/mpvue@6c5d78ee04 (2026-09-02). Data as JSON: /api/errors/904f23202213efb3. Report an issue: GitHub.