LABjs-lite/lab.js at master · silenaker/LABjs-lite · GitHub

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(function (window) {
  var scriptsCache = {};

  function LAB() {
    var curCbs = [];
    var curErrHandles = [];
    var syncReqQueCbs = [];
    var syncErrHandles = [];
    var syncReqQue = [];
    var loadingNum = 0;
    var queIdx = -1;

    function nonOperate() {}

    function triggerCallbacks(err) {
      if (err) {
        errHandle(err);
      } else {
        try {
          while (curCbs.length) {
            curCbs.shift().call(null);
          }
        } catch (e) {
          errHandle(e);
        }
      }
      curCbs = curErrHandles = [];
      curCbs.push.apply(curCbs, syncReqQueCbs.shift());
      curErrHandles.push.apply(curErrHandles, syncErrHandles.shift());
      (nextReqs = syncReqQue.shift()) && nextReqs.forEach(function (request) {
        request();
      });

      function errHandle(err) {
        if (!curErrHandles.length) throw new Error(err);
        while (curErrHandles.length) {
          curErrHandles.shift().call(null, err);
        }
      }
    }

    function _load(url, callback) {
      if (scriptsCache[url] && !scriptsCache[url].loaded) return;
      if (scriptsCache[url] && scriptsCache[url].loaded) {
        setTimeout(function () {
          callback();
        });
        return;
      }
      document = window.document;
      var head = document.getElementsByTagName('head')[0];
      var script = document.createElement('script');
      script.type = 'text/javascript';
      script.charset = 'utf-8';
      script.async = true;
      script.src = url;
      script.onerror = function () {
        delete scriptsCache[url];
        script.remove();
        callback({
          msg: 'err',
          url: url
        });
      }
      script.onload = function () {
        scriptsCache[url].loaded = 1;
        callback();
      }
      head.appendChild(script);
      setTimeout(function () {
        if (scriptsCache[url].loaded === 0) {
          delete scriptsCache[url];
          script.remove();
          callback({
            msg: 'timeout',
            url: url
          });
        }
      }, 5000);
      scriptsCache[url] = {
        loaded: 0
      };
    }

    function load(url) {
      loadingNum++;
      _load(url, function (err) {
        if (err) {
          loadingNum = 0;
          triggerCallbacks(err);
        }
        if (loadingNum > 0) {
          loadingNum--
          if (!loadingNum) {
            triggerCallbacks();
          }
        }

      });
    }

    return {
      script: function (url) {
        if (curCbs.length) {
          if (queIdx === -1 || syncReqQueCbs[queIdx]) {
            syncReqQue[++queIdx] = [];
          }
          syncReqQue[queIdx].push(function () {
            load(url);
          });
        } else {
          load(url);
        }
        return this;
      },
      wait: function (fn) {
        fn = fn || nonOperate;
        if (queIdx === -1) {
          curCbs.push(fn);
        } else {
          if (!syncReqQueCbs[queIdx]) {
            syncReqQueCbs[queIdx] = [];
          }
          syncReqQueCbs[queIdx].push(fn);
        }
        return this;
      },
      catch: function (fn) {
        if (queIdx === -1) {
          curErrHandles.push(fn);
        } else {
          if (!syncErrHandles[queIdx]) {
            syncErrHandles[queIdx] = [];
          }
          syncErrHandles[queIdx].push(fn);
        }
        return this;
      }
    }
  }
  window.$LAB = LAB;
})(window);