this.$refs.pullScroll.refresh();这个方法一直报错，我用在了H5的页面上，

this.$refs.pullScroll.refresh();这个方法一直报错，我用在了H5的页面上，
报错内容：
index.umd.min.js?1c31:1 [system] TypeError: _this.$refs.pullScroll.refresh is not a function
at VueComponent.eval (eval at ./node_modules/babel-loader/lib/index.js!./node_modules/@dcloudio/vue-cli-plugin-uni/packages/webpack-preprocess-loader/index.js?!./node_modules/@dcloudio/vue-cli-plugin-uni/packages/webpack-preprocess-loader/index.js?!./node_modules/@dcloudio/vue-cli-plugin-uni/packages/webpack-uni-app-loader/using-components.js!./node_modules/@dcloudio/vue-cli-plugin-uni/packages/vue-loader/lib/index.js?!./node_modules/@dcloudio/vue-cli-plugin-uni/packages/webpack-scoped-loader/index.js!../../../../Users/84960/Desktop/选项卡/第3个下拉刷新，上拉加载 s-pull-scroll示例/pages/pull-scroll/index.vue?vue&type=script&lang=js& (pages-pull-scroll-index.2a88af778ed000230346.hot-update.js:23), <anonymous>:79:128)
at Array.eval (vue.runtime.esm.js?e143:1991)
at flushCallbacks (vue.runtime.esm.js?e143:1917)
at <anonymous>
(anonymous) @ index.umd.min.js?1c31:1
e.onError.length.e.onError @ index.umd.min.js?1c31:1
invokeWithErrorHandling @ vue.runtime.esm.js?e143:1865
Vue.call_hook @ vue.runtime.esm.js?e143:8615
e.config.errorHandler @ index.umd.min.js?1c31:1
globalHandleError @ vue.runtime.esm.js?e143:1881
handleError @ vue.runtime.esm.js?e143:1850
(anonymous) @ vue.runtime.esm.js?e143:1993
flushCallbacks @ vue.runtime.esm.js?e143:1917
Promise.then (async)
timerFunc @ vue.runtime.esm.js?e143:1944
nextTick @ vue.runtime.esm.js?e143:2001
Vue.$nextTick @ vue.runtime.esm.js?e143:3572
doRefresh @ index.vue?a730:58
onLoad @ index.vue?a730:46
invokeWithErrorHandling @ vue.runtime.esm.js?e143:1865
Vue.__call_hook @ vue.runtime.esm.js?e143:8615
r @ index.umd.min.js?1c31:1
a @ index.umd.min.js?1c31:1
created @ index.umd.min.js?1c31:1
invokeWithErrorHandling @ vue.runtime.esm.js?e143:1865
callHook @ vue.runtime.esm.js?e143:4276
Vue._init @ vue.runtime.esm.js?e143:5065
VueComponent @ vue.runtime.esm.js?e143:5211
createComponentInstanceForVnode @ vue.runtime.esm.js?e143:3334
init @ vue.runtime.esm.js?e143:3163
createComponent @ vue.runtime.esm.js?e143:6035
createElm @ vue.runtime.esm.js?e143:5982
updateChildren @ vue.runtime.esm.js?e143:6273
patchVnode @ vue.runtime.esm.js?e143:6376
updateChildren @ vue.runtime.esm.js?e143:6250
patchVnode @ vue.runtime.esm.js?e143:6376
patch @ vue.runtime.esm.js?e143:6539
Vue._update @ vue.runtime.esm.js?e143:3999
updateComponent @ vue.runtime.esm.js?e143:4117
get @ vue.runtime.esm.js?e143:4536
run @ vue.runtime.esm.js?e143:4611
flushSchedulerQueue @ vue.runtime.esm.js?e143:4367
(anonymous) @ vue.runtime.esm.js?e143:1991
flushCallbacks @ vue.runtime.esm.js?e143:1917
Promise.then (async)
timerFunc @ vue.runtime.esm.js?e143:1944
nextTick @ vue.runtime.esm.js?e143:2001
queueWatcher @ vue.runtime.esm.js?e143:4459
update @ vue.runtime.esm.js?e143:4601
Vue.$forceUpdate @ vue.runtime.esm.js?e143:4020
(anonymous) @ index.js?6435:236
(anonymous) @ index.js?6435:234
(anonymous) @ index.js?6435:119
(anonymous) @ index.vue?05f0:32
../../../../Users/84960/Desktop/选项卡/第3个下拉刷新，上拉加载 s-pull-scroll示例/pages/pull-scroll/index.vue @ pages-pull-scroll-index.js:23
webpack_require__ @ index.js:767
hotApply @ index.js:686
(anonymous) @ index.js:343
Promise.then (async)
hotUpdateDownloaded @ index.js:342
hotAddUpdateChunk @ index.js:318
webpackHotUpdateCallback @ index.js:37
(anonymous) @ pages-pull-scroll-index.2a88af778ed000230346.hot-update.js:1