fetch跨域問題

 fetch(url,{
        method:'post', 
        mode:"cors",      //容許跨域  no-cors不容許跨域
      //  credentials:"include",  //跨域請求時是不帶cookie的，添加該屬性表示強制加入憑據頭,請求時就會攜帶cookie。可是若是加上這個屬性，那麼服務器的Access-Control-Allow-Origin 就不能是‘*’，不然會報下面的錯誤。
        headers:new Headers({
         'Content-Type': 'application/x-www-form-urlencoded', // 指定提交方式爲表單提交
          }),
          body:formdate
        }) .then(function(response) {
    
    return response.json();

  }).then(function(json) {
    console.log('parsed json', json);
    
  }).catch(function(ex) {
    console.log('parsing failed', ex);
   
  })

跨域設置credentials:"include"時，若是服務器端設置Access-Control-Allow-Origin 爲‘*’會報以下錯誤。能夠去掉該請求頭的設置，只添加mode:'cors'屬性。

The value of the 'Access-Control-Allow-Origin' header in the response must not be the wildcard '*' when the request's credentials mode is 'include'. Origin 'http://localhost:8080' is therefore not allowed access.