Fetch Example application/x-www-form

fetchPostForm.js

let customSearch = (params) => {
    let url = '/contentlicenseajax';
    let body = Object.keys(params)
                .map((key) => { return encodeURIComponent(key) + '=' + encodeURIComponent(params[key]); })
                .join('&');
    return fetch('/contentlicenseajax', {
                                        method: 'POST',
                                        headers: { 'Content-Type': 'application/x-www-form-urlencoded;charset=UTF-8' },
                                        credentials: 'include',
                                        body: body
                                        })
      .then(res => res.json()).catch(res => Promise.fail({error:res}));
};