clean up and documentation

server/lib/api_helper.js

@@ -0,0 +1,29 @@
+class ApiHelper {
+
+  // assume all dates from api coming as UNIX timestamps.
+  static datesParamToSequelize(dates, field_name){
+    if (!dates) return {};
+    var params = {};
+
+    if (dates.length > 1){
+      params['$or'] = [];
+      dates.forEach((min_max)=>{
+        var condition_n = {};
+        condition_n[field_name] = {};
+        if (min_max[0]) condition_n[field_name]['$gte'] = min_max[0];
+        if (min_max[1]) condition_n[field_name]['$lte'] = min_max[1];
+        if (Object.keys(condition_n).length) params['$or'].push(condition_n);
+      });
+    } else {
+      var min_max = dates[0],
+        condition = {}
+      if (min_max[0]) condition['$gte'] = min_max[0];
+      if (min_max[1]) condition['$lte'] = min_max[1];
+      if (Object.keys(condition).length) params[field_name] = condition;
+    }
+    return params;
+  }
+
+}
+
+export default ApiHelper;