Function snapshotComparator

test/BasicQueryableMemoryDB.js:70–91

(sortProperties)

// sortProperties is an array whose items are each [propertyName, direction].
function snapshotComparator(sortProperties) {
  return function(snapshotA, snapshotB) {
    for (var i = 0; i < sortProperties.length; i++) {
      var sortProperty = sortProperties[i];
      var sortKey = sortProperty[0];
      var sortDirection = sortProperty[1];

      var aPropVal = snapshotA.data[sortKey];
      var bPropVal = snapshotB.data[sortKey];
      if (aPropVal < bPropVal) {
        return -1 * sortDirection;
      } else if (aPropVal > bPropVal) {
        return sortDirection;
      } else if (aPropVal === bPropVal) {
        continue;
      } else {
        throw new Error('Could not compare ' + aPropVal + ' and ' + bPropVal);
      }
    }
    return 0;
  };
}