在登入页面，我们往往需要通过输入验证码才能进行登入，那我们下面就详讲一下在vue项目中如何配合element-ui实现这个功能

第一步：自定义一个生产随机验证码的组件，其本质是使用canvas绘制，详细代码如下：

<template>
  <div class="s-canvas">
    <canvas id="s-canvas" :width="contentWidth" :height="contentHeight"></canvas>
  </div>
</template>
<script>
export default {
  name: 'SIdentify',
  props: {
    identifyCode: {
      type: String,
      default: '1234'
    },
    fontSizeMin: {
      type: Number,
      default: 16
    },
    fontSizeMax: {
      type: Number,
      default: 40
    },
    backgroundColorMin: {
      type: Number,
      default: 180
    },
    backgroundColorMax: {
      type: Number,
      default: 240
    },
    colorMin: {
      type: Number,
      default: 50
    },
    colorMax: {
      type: Number,
      default: 160
    },
    lineColorMin: {
      type: Number,
      default: 40
    },
    lineColorMax: {
      type: Number,
      default: 180
    },
    dotColorMin: {
      type: Number,
      default: 0
    },
    dotColorMax: {
      type: Number,
      default: 255
    },
    contentWidth: {
      type: Number,
      default: 112
    },
    contentHeight: {
      type: Number,
      default: 38
    }
  },
  methods: {
    // 生成一个随机数
    randomNum(min, max) {
      return Math.floor(Math.random() * (max - min) + min)
    },
    // 生成一个随机的颜色
    randomColor(min, max) {
      var r = this.randomNum(min, max)
      var g = this.randomNum(min, max)
      var b = this.randomNum(min, max)
      return 'rgb(' + r + ',' + g + ',' + b + ')'
    },
    drawPic() {
      var canvas = document.getElementById('s-canvas')
      var ctx = canvas.getContext('2d')
      ctx.textBaseline = 'bottom'
      // 绘制背景
      ctx.fillStyle = this.randomColor(
        this.backgroundColorMin,
        this.backgroundColorMax
      )
      ctx.fillRect(0, 0, this.contentWidth, this.contentHeight)
      // 绘制文字
      for (let i = 0; i < this.identifyCode.length; i++) {
        this.drawText(ctx, this.identifyCode[i], i)
      }
      this.drawLine(ctx)
      this.drawDot(ctx)
    },
    drawText(ctx, txt, i) {
      ctx.fillStyle = this.randomColor(this.colorMin, this.colorMax)
      ctx.font =
        this.randomNum(this.fontSizeMin, this.fontSizeMax) + 'px SimHei'
      var x = (i + 1) * (this.contentWidth / (this.identifyCode.length + 1))
      var y = this.randomNum(this.fontSizeMax, this.contentHeight - 5)
      var deg = this.randomNum(-45, 45)
      // 修改坐标原点和旋转角度
      ctx.translate(x, y)
      ctx.rotate(deg * Math.PI / 180)
      ctx.fillText(txt, 0, 0)
      // 恢复坐标原点和旋转角度
      ctx.rotate(-deg * Math.PI / 180)
      ctx.translate(-x, -y)
    },
    drawLine(ctx) {
      // 绘制干扰线
      for (let i = 0; i < 8; i++) {
        ctx.strokeStyle = this.randomColor(
          this.lineColorMin,
          this.lineColorMax
        )
        ctx.beginPath()
        ctx.moveTo(
          this.randomNum(0, this.contentWidth),
          this.randomNum(0, this.contentHeight)
        )
        ctx.lineTo(
          this.randomNum(0, this.contentWidth),
          this.randomNum(0, this.contentHeight)
        )
        ctx.stroke()
      }
    },
    drawDot(ctx) {
      // 绘制干扰点
      for (let i = 0; i < 100; i++) {
        ctx.fillStyle = this.randomColor(0, 255)
        ctx.beginPath()
        ctx.arc(
          this.randomNum(0, this.contentWidth),
          this.randomNum(0, this.contentHeight),
          1,
          0,
          2 * Math.PI
        )
        ctx.fill()
      }
    }
  },
  watch: {
    identifyCode() {
      this.drawPic()
    }
  },
  mounted() {
    this.drawPic()
  }
}
</script>

第二步：使用该组件：

我们首先新建一个vue组件，在该组件进行布局，其中还包括用户名和密码的验证（这只是前端的简单验证，真实项目中还需要请求登入接口进行后端验证）

<template>
  <el-form class="login-form" status-icon :rules="loginRules" ref="loginForm" :model="loginForm" label-width="0">
    <el-form-item prop="username">
      <el-input size="small" @keyup.enter.native="handleLogin" v-model="loginForm.username" auto-complete="off" placeholder="请输入用户名">
        <i slot="prefix" class="icon-yonghu"></i>
      </el-input>
    </el-form-item>
    <el-form-item prop="password">
      <el-input size="small" @keyup.enter.native="handleLogin" :type="passwordType" v-model="loginForm.password" auto-complete="off" placeholder="请输入密码">
        <i class="el-icon-view el-input__icon" :style="fontstyle" slot="suffix" @click="showPassword"></i>
        <i slot="prefix" class="icon-mima"></i>
      </el-input>
    </el-form-item>
    <el-form-item  prop="verifycode">
      <!-- 注意：prop与input绑定的值一定要一致，否则验证规则中的value会报undefined，因为value即为绑定的input输入值 -->
      <el-input v-model="loginForm.verifycode" placeholder="请输入验证码" class="identifyinput"></el-input>
    </el-form-item>
    <el-form-item>
      <div class="identifybox">
        <div @click="refreshCode">
          <s-identify :identifyCode="identifyCode"></s-identify>
        </div>
        <el-button @click="refreshCode" type='text' class="textbtn">看不清，换一张</el-button>
      </div>
    </el-form-item>
    <el-checkbox v-model="checked">记住账号</el-checkbox>
    <el-form-item>
      <el-button type="primary" size="small" @click.native.prevent="handleLogin" class="login-submit">登录</el-button>
    </el-form-item>
  </el-form>
</template>

 第三步：生产随机码与进行登入验证

<script>
import { isvalidUsername } from '@/utils/validate'
import SIdentify from '@/components/identify/identify.vue'
export default {
  name: 'userlogin',
  data() {
    // 用户名自定义验证规则
    const validateUsername = (rule, value, callback) => {
      if (!isvalidUsername(value)) {
        callback(new Error('请输入正确的用户名'))
      } else {
        console.log('user', value)
        callback()
      }
    }
    // 验证码自定义验证规则
    const validateVerifycode = (rule, value, callback) => {
      if (value === '') {
        callback(new Error('请输入验证码'))
      } else if (value !== this.identifyCode) {
        console.log('validateVerifycode:', value)
        callback(new Error('验证码不正确!'))
      } else {
        callback()
      }
    }
    return {
      fontstyle: {
      },
      loginForm: {
        username: 'admin',
        password: '123456',
        verifycode: ''
      },
      checked: false,
      identifyCodes: '1234567890',
      identifyCode: '',
      loginRules: { // 绑定在form表单中的验证规则
        username: [
          { required: true, trigger: 'blur', validator: validateUsername }
        ],
        password: [
          { required: true, message: '请输入密码', trigger: 'blur' },
          { min: 6, message: '密码长度最少为6位', trigger: 'blur' }
        ],
        verifycode: [
          { required: true, trigger: 'blur', validator: validateVerifycode }
        ]
      },
      passwordType: 'password'
    }
  },
  components: {
    SIdentify
  },
  created() {
  },
  mounted() {
    // 验证码初始化
    this.identifyCode = ''
    this.makeCode(this.identifyCodes, 4)
  },
  computed: {
  },
  props: [],
  methods: {
    // 通过改变input的type使密码可见
    showPassword() {
      this.fontstyle === '' ? (this.fontstyle = 'color: red') : (this.fontstyle = '') // 改变密码可见按钮颜色
      this.passwordType === ''
        ? (this.passwordType = 'password')
        : (this.passwordType = '')
    },
    // 点击登入按钮
    handleLogin() {
      this.$refs.loginForm.validate(valid => {
        if (valid) {
          this.$store.dispatch('Login', this.loginForm).then(res => {
            this.$router.push({ path: '/dashboard/dashboard' })
          })
        }
      })
    },
    // 生成随机数
    randomNum(min, max) {
      return Math.floor(Math.random() * (max - min) + min)
    },
    // 切换验证码
    refreshCode() {
      this.identifyCode = ''
      this.makeCode(this.identifyCodes, 4)
    },
    // 生成四位随机验证码
    makeCode(o, l) {
      for (let i = 0; i < l; i++) {
        this.identifyCode += this.identifyCodes[
          this.randomNum(0, this.identifyCodes.length)
        ]
      }
      console.log(this.identifyCode)
    }
  }
}
</script>
<style scoped>
.identifybox{
  display: flex;
  justify-content: space-between;
  margin-top:7px;
}
.iconstyle{
  color:#409EFF;
}
</style>

最后的效果如下，当我们输入之后鼠标失去焦点就会进行验证：