vue-cli下axios实现跨域踩的坑

按踩坑顺序叙述。本人对http了解太少，所以坑踩得较多。 
1.开始进行跨域时，知道vue2.0官方推荐axios进行ajax请求，大致看一下https://www.npmjs.com/package/axios axios的用法，感觉挺好理解嘛，封装的挺好，用时发现，不对啊。跨域设置在哪？最后找到了它

proxyTable: {
   '/shopping':{//此处并非一定和url一致。
      target:'https://mainsite-restapi.ele.me/shopping',
      changeOrigin:true,//允许跨域
      pathRewrite:{
        '^/shopping': ''
      }
    }
}
此段代码表示，如果请求地址以/login开头，则自动加上target。
如：/shopping/v2/restaurant/category  等于
https://mainsite-restapi.ele.me/shopping/v2/restaurant/category
设置成功，感觉axios就是方便。走着走着发现。。。不对

2.get请求成功，换成post请求。坑爹啊

:8000/#/login:1 XMLHttpRequest cannot load http://cunguan.com/index.php?user&q=action/login. No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://localhost:8000' is therefore not allowed access.

查了半天发现直接访问接口时，要对后端响应头进行设置（最后发现如果用1中的方法进行跨域访问设置则不需要在后端添加响应头）

// 指定允许其他域名访问
header("Access-Control-Allow-Origin:*");
// 响应类型
header("Access-Control-Allow-Methods:POST");
// 响应头设置
header("Access-Control-Allow-Headers:x-requested-with,content-type");
添加完毕，好了错没了，可发现数据好像有问题啊。我访问的是自己的接口，因为是以前的老接口，不能改所以只有硬着头皮改前台了

3.以前的请求参数为form data怎么这次请求神奇的变为request payload，崩溃中，最后找到要添加Content-Type：application/x-www-form-urlencoded

headers: {
     'Content-Type': 'application/x-www-form-urlencoded'
}
this.$http.post('/login/index.php?user&q=action/login', {'a': 'test', 'b': '123456'}), {
          headers: {
            'Content-Type': 'application/x-www-form-urlencoded'
          }
})
    .then(function (response) {
       console.log(response)
     })
     .catch(function (error) {
       console.log(error)
     })
好吧  请求默认的需要修改我认了，改过之后发现。。。我参数呢？这次好了，参数都丢了继续查文档吧

4.Content-Type：application/x-www-form-urlencoded 时参数格式的问题下面摘自 
https://github.com/mzabriskie/axios/blob/master/README.md#using-applicationx-www-form-urlencoded-format. 下面三种技能，我用了一种，轻松搞定。

Using application/x-www-form-urlencoded format

By default, axios serializes JavaScript objects to JSON. To send data in the application/x-www-form-urlencoded format instead, you can use one of the following options.

**Browser**

In a browser, you can use the URLSearchParams API as follows:

    var params = new URLSearchParams();
    params.append('param1', 'value1');
    params.append('param2', 'value2');
    axios.post('/foo', params);
Note that URLSearchParams is not supported by all browsers, but there is a polyfill available (make sure to polyfill the global environment).
Alternatively, you can encode data using the qs library:

    var qs = require('qs');
    axios.post('/foo', qs.stringify({ 'bar': 123 }));

Node.js

In node.js, you can use the querystring module as follows:

    var querystring = require('querystring');
    axios.post('http://something.com/', querystring.stringify({ foo: 'bar' }));

You can also use the qs library.

如果到这还没解决你的问题，不好意思，go for it 哈哈哈