element-plus/packages/locale/index.ts

import defaultLang from './lang/zh-CN'
import Vue from 'vue'
import deepmerge from 'deepmerge'
import Format from './format'

const format = Format(Vue)
let lang = defaultLang
let merged = false
let i18nHandler = function(...args) {
  const vuei18n = Object.getPrototypeOf(this || Vue).$t
  if (typeof vuei18n === 'function' && !!Vue.locale) {
    if (!merged) {
      merged = true
      Vue.locale(
        Vue.config.lang,
        deepmerge(lang, Vue.locale(Vue.config.lang) || {}, { clone: true }),
      )
    }
    return vuei18n.apply(this, args)
  }
}

export const t = function(path, options, ...args) {
  let value = i18nHandler.apply(this, [path, options, args])
  if (value !== null && value !== undefined) return value

  const array = path.split('.')
  let current = lang

  for (let i = 0, j = array.length; i < j; i++) {
    const property = array[i]
    value = current[property]
    if (i === j - 1) return format(value, options)
    if (!value) return ''
    current = value
  }
  return ''
}

export const use = function(l) {
  lang = l || lang
}

export const i18n = function(fn) {
  i18nHandler = fn || i18nHandler
}

export default { use, t, i18n }