官网说的是这样的：

 

但实际上，应该是这样修改：

{  "presets": [    ["env", {      "targets": {        "browsers": ["> 1%", "last 2 versions", "not ie <= 8"]      }    }],    "stage-2"  ],  "plugins": [      "transform-vue-jsx",       "transform-runtime",      ["component", {          "libraryName": "element-ui",        "styleLibraryName": "theme-chalk"      }]   ]}