9种跨域方案

jsonp

**

function jsonp ({url, params, cb}) {
        return new Promise((resolve, reject) => {
            let script = document.createElement('script');
            window[cb] = function(data) {
                resolve(data);
                document.body.removeChild(script)
            }
            params = {...params, cb};
            let arr = [];  //wd=爱奇艺&cb=show
            for(var key in params){
                arr.push(`${key}=${params[key]}`);
            }
            if(url.indexOf('?') > -1){
                script.src = `${url}&${arr.join('&')}`;
            }else{
                script.src = `${url}?${arr.join('&')}`;
            }
            document.body.appendChild(script);
        })
    }
    // 只能发送get请求 不支持post put delect
    // xss攻击 不安全
    jsonp({
        url: 'https://www.baidu.com/sugrec?prod=pc&from=pc_web',
        params: {
            wd: '美妆'
        },
        cb: 'show'
    })