var is a reserved word

1、错误描述

PieChart.vue?a6c7:69 Uncaught (in promise) TypeError: Cannot read property '$el' of undefined
    
at PieChart.vue?a6c7:69
client:162 [WDS] Errors while compiling. Reload prevented.
errors 
@ client:162
onmessage 
@ socket.js:41
EventTarget.dispatchEvent 
@ sockjs.js:170
(anonymous) 
@ sockjs.js:887
SockJS._transportMessage 
@ sockjs.js:885
EventEmitter.emit 
@ sockjs.js:86
WebSocketTransport.ws.onmessage 
@ sockjs.js:2961
client:168 ./src/views/dashboard/admin/components/PieChart.vue?vue&type=script&lang=js& (./node_modules/babel-loader/lib?cacheDirectory!./node_modules/vue-loader/lib??vue-loader-options!./src/views/dashboard/admin/components/PieChart.vue?vue&type=script&lang=js&)
Module build failed (from ./node_modules/babel-loader/lib/index.js):
SyntaxError: F:/dojo/cdmn/vue-element-admin/src/views/dashboard/admin/components/PieChart.vue: var is a reserved word (49:4)

  47 |   },
  48 |   methods: {
> 49 |     var that = this,
     |     ^
  50 |     initChart() {
  51 |       axios.get('/api/manage/common/cmp',{
  52 |         
params:{

errors @ client:168
onmessage @ socket.js:41
EventTarget.dispatchEvent @ sockjs.js:170
(anonymous) @ sockjs.js:887
SockJS._transportMessage @ sockjs.js:885
EventEmitter.emit @ sockjs.js:86
WebSocketTransport.ws.onmessage @ sockjs.js:2961
client:162 [WDS] Errors while compiling. Reload prevented.
errors @ client:162
onmessage @ socket.js:41
EventTarget.dispatchEvent @ sockjs.js:170
(anonymous) @ sockjs.js:887
SockJS._transportMessage @ sockjs.js:885
EventEmitter.emit @ sockjs.js:86
WebSocketTransport.ws.onmessage @ sockjs.js:2961
client:168 ./src/views/dashboard/admin/components/PieChart.vue?vue&type=script&lang=js& (./node_modules/babel-loader/lib?cacheDirectory!./node_modules/vue-loader/lib??vue-loader-options!./src/views/dashboard/admin/components/PieChart.vue?vue&type=script&lang=js&)
Module build failed (from ./node_modules/babel-loader/lib/index.js):
SyntaxError: F:/dojo/cdmn/vue-element-admin/src/views/dashboard/admin/components/PieChart.vue: var is a reserved word (49:4)

  47 |   },
  48 |   methods: {
> 49 |     var that = this,
     |     ^
  50 |     initChart() {
  51 |       axios.get('/api/manage/common/cmp',{
  52 |         params:{

2、错误原因

      在vue.js中的methods，定义that=this，这个语句应该放在initChart方法中

methods: {
    var that = this,
    initChart(){

    }
}

3、解决办法

      调换变量定义的位置

methods: {
    initChart(){
       var that = this
    }
}