micro ajax 'library' wrapping XMLHttpRequest in a Promise. 315 bytes before compression.

_src.js

/*
  Usage ::
    const url = "http://httpbin.org/post",
          body = JSON.stringify({foo: "bar"}),
          timeout = 5000; // 5 seconds
    
    rq(url, {m:"POST", b:body, t:timeout})
    .then(xhr => console.log(xhr.response))
    .catch(xhr => console.log("Failed to load " + url));
*/

/*
  u :: "https://google.com"        // url **required**
  opts :: {
      m: "GET",                    // method       (defaults to GET)
      h: {"content-length": "3"},  // headers      (defaults to none)
      r: "json",                   // responseType (defaults to json)
      t: 5000,                     // timeout (ms) (defaults to unlimited)
      b: {userId: "foo"},          // body         (defaults to undefined)
  }
  x :: reserved
*/
rq = (u, opts, x) => {
    x = new XMLHttpRequest;
    x.open(opts.m || "GET", u);
    x.responseType = opts.r || "";
    x.timeout = opts.t || 0;
    Object.keys(opts.h || 0).forEach(h => x.setRequestHeader(h, opts.h[h]));

    return new Promise((y,n) => {
        x.onreadystatechange = _=>{
            x.readyState==4 && [n,y][(!!x.response && (x.status/200|0)==1)|0](x);
        };
        x.ontimeout = _=>n(x);
        x.send(opts.b || undefined);
    })
};

index.js

rq=(c,b,a)=>{a=new XMLHttpRequest;a.open(b.m||"GET",c);a.responseType=b.r||"";a.timeout=b.t||0;Object.keys(b.h||0).forEach(c=>a.setRequestHeader(c,b.h[c]));return new Promise((c,d)=>{a.onreadystatechange=b=>{4==a.readyState&&[d,c][(!!a.response&&1==(a.status/200|0))|0](a)};a.ontimeout=b=>d(a);a.send(b.b||[]._)})};

LICENSE.txt

            DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
                    Version 2, December 2004

 Copyright (C) 2016 Joe Cross

 Everyone is permitted to copy and distribute verbatim or modified
 copies of this license document, and changing it is allowed as long
 as the name is changed.

            DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
   TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION

0. You just DO WHAT THE FUCK YOU WANT TO.