enhance sorting logic for mixed type columns

Author: ibdafna

src/core/transformExecutors.ts

@@ -248,14 +248,31 @@ export class SortExecutor extends TransformExecutor {
   public apply(input: TransformExecutor.IData): TransformExecutor.IData {
     let sortFunc: (a: any, b: any) => number;
     const field = this._options.field;
+    const columnDataType = this._options.dType;
+
+    // Adding string checks within the sort function so we do
+    // not have to mutate in-place the original types of the
+    // values of the column into strings. This allows the
+    // displayed values to maintain their original types but
+    // be sorted as if they were all strings.
+    const stringifyIfNeeded = (value: any) => {
+      if (typeof value != 'string' && columnDataType == 'string') {
+        return String(value);
+      }
+      return value;
+    };
 
     if (this._options.desc) {
       sortFunc = (a: any, b: any): number => {
-        return a[field] < b[field] ? 1 : -1;
+        return stringifyIfNeeded(a[field]) < stringifyIfNeeded(b[field])
+          ? 1
+          : -1;
       };
     } else {
       sortFunc = (a: any, b: any): number => {
-        return a[field] > b[field] ? 1 : -1;
+        return stringifyIfNeeded(a[field]) > stringifyIfNeeded(b[field])
+          ? 1
+          : -1;
       };
     }