Vue.use()的用法和install的用法解析

目录

• Vue.use()和install用法
• 介绍
• 为什么这样做？
• Vue.use为什么要使用install
• 疑问
• 从源码分析
• vue官网是这样说的

import ElementUI from "element-ui"
import "element-ui/lib/theme-chalk/index.css"
Vue.use(ElementUI)

// Vue源码文件路径：src/core/shared/util.js
export function toArray (list: any, start?: number): Array {
  start = start || 0
  let i = list.length - start
  const ret: Array = new Array(i)
  while (i--) {
    ret[i] = list[i + start]
  }
  return ret
}

// Vue源码文件路径：src/core/global-api/use.js
import { toArray } from "../util/index"
export function initUse (Vue: GlobalAPI) {
  Vue.use = function (plugin: Function | Object) {
    const installedPlugins = (this._installedPlugins || (this._installedPlugins = []))
    if (installedPlugins.indexOf(plugin) > -1) { // 如果该插件已被注册，则不再进行注册
      return this
    }
    // additional parameters
    const args = toArray(arguments, 1)
    args.unshift(this)
    if (typeof plugin.install === "function") {
      plugin.install.apply(plugin, args)
    } else if (typeof plugin === "function") {
      plugin.apply(null, args)
    }
    installedPlugins.push(plugin)
    return this
  }
}