app.js全局数据中添加header

  globalData: {
    userInfo: null,
    header: {
      'Cookie': ''
    }
  }

test.js

const app = getApp()

Page({
   data: {
     imgUrl: '' ,
     result: ''
   },
   onLoad() {
     this .initCaptcha();
   },
   initCaptcha() {
     let url = '{域名}/Captcha/Index' ; // 空请求 为了拿到sessionId
     wx.request({
       header: app.globalData.header,
       url,
       data:{},
       success: (res) => {
         this .setSessionId(res);
         this .downloadCaptcha();
       }
     })
   },
   downloadCaptcha(){
     let url = '{域名}/Captcha/Generate?' + new Date().getTime();
     wx.downloadFile({
       header: app.globalData.header, // down时是没有sessionId
       url,
       success: (res) => {
         console.log(res);
         this .setData({
           imgUrl:res.tempFilePath
         });
       }
     })
   },
   refreshCaptcha() {
     this .initCaptcha();
   },

   setSessionId(res) {
     let cookieStr = res.header[ 'Set-Cookie' ];
     // app.globalData.header.Cookie = cookieStr;
     if (cookieStr){
       let cookies = cookieStr.split( '; ' )

       if (!cookies || cookies.length <= 0)
         return ;

       cookies.forEach(
         (v) => {
           const str = v.split( '=' );
           if (str[0] && str[0] == 'PHPSESSID' ) {
             let sessionId = decodeURI(str[1]);
             app.globalData.header.Cookie = `PHPSESSID=${sessionId}`;
           }
         }
       );
     }

   },

   onSubmit(e){
     let { code } = e.detail.value;
     let url = '{域名}/Captcha/Validate' ;
     wx.request({
       header: app.globalData.header,
       url,
       data: {code},
       success: (res) => {
         console.log(res);
         this .initCaptcha();

         this .setData({
           result:res.data.message
         })
       }
     })
   }
})

相关资料

微信小程序可以用thinkphp的验证码类库captcha来做图形验证码
微信小程序Session问题