A jsonp function

jsonp.js

function jsonp(options) {
  options = options || {};
  if (!options.url || !options.jsonp) {
    throw new Error('参数不合法');
  }

  options.data = options.data || {};

  // 创建 script
  var callbackName = ('jsonp_' + Math.random()).replace('.', '');
  options.data[options.jsonp] = callbackName;
  var params = formatParams(options.data);
  var head = document.getElementsByTagName('head')[0];
  var script = document.createElement('script');
  head.appendChild(script);

  // 创建回调
  window[callbackName] = function (json) {
    clearTimeout(script._timeId);
    script._timeId = null;
    head.removeChild(script);
    window[callbackName] = null;
    delete window[callbackName];
    options.success && options.success(json);
  }

  // 发送请求
  script.src = options.url.indexOf('?') > 0 ? (options.url + '&' + params) : (options.url + '?' + params);

  // 超时处理
  if (options.timeout) {
    script._timeId = setTimeout(function () {
      script._timeId = null;
      head.removeChild(script);
      window[callbackName] = null;
      delete window[callbackName];
      options.fail && options.fail({ message: '请求超时' });
    }, options.timeout);
  }

  function formatParams(data) {
    var arr = [];
    for (var name in data) {
      arr.push(encodeURIComponent(name) + '=' + encodeURIComponent(data[name]));
    }

    return arr.join('&');
  }
}