Firebase Promise Wrappers

gistfile1.js

  // Get Firebase value from a query as a Promise.
  function getValue(ref, allowNull) {
    return new Promise(function(resolve, reject) {
      ref.once('value',
               function(snap) {
                 var result = snap.val();
                 if (result === null && !allowNull) {
                   reject(new Error("No data at location: " + ref.toString()));
                   return;
                 }
                 resolve(result);
               },
               function(error) {
                 reject(new Error(error.toString()));
               });
    });
  }

  function setValue(ref, value) {
    return new Promise(function(resolve, reject) {
      ref.set(value, function(error) {
        if (error === null) {
          resolve(true);
        } else {
          reject(new Error(error.toString()));
        }
      });
    });
  }

  function pushValue(ref, value) {
    return new Promise(function(resolve, reject) {
      var pushRef = ref.push(value, function(error) {
        if (error === null) {
          resolve(pushRef);
        } else {
          reject(new Error(error.toString()));
        }
      });
    });
  }