Added error message when both round and precision used

Author: ankane

examples/index.html

@@ -682,6 +682,12 @@ <h1>Precision - Small</h1>
       new Chartkick.ColumnChart("precision-small", [["A",1.2345],["B",0.12345],["C",0.012345]], {precision: 3});
     </script>
 
+    <h1>Round and Precision</h1>
+    <div id="round-precision" style="height: 300px;"></div>
+    <script>
+      new Chartkick.ColumnChart("round-precision", [["A",1.2345],["B",0.12345],["C",0.012345]], {round: 2, precision: 3});
+    </script>
+
     <h1>Null Data</h1>
     <div id="null-data" style="height: 300px;"></div>
     <script>

src/helpers.js

@@ -235,6 +235,7 @@ function formatValue(pre, value, options, axis) {
 
   let suffix = options.suffix || "";
   let precision = options.precision;
+  let round = options.round;
 
   if (options.byteScale) {
     let baseValue = axis ? options.byteScale : value;
@@ -254,23 +255,27 @@ function formatValue(pre, value, options, axis) {
       suffix = " bytes";
     }
 
-    if (precision === undefined) {
+    if (precision === undefined && round === undefined) {
       precision = 3;
     }
   }
 
+  if (precision !== undefined && round !== undefined) {
+    throw Error("Use either round or precision, not both");
+  }
+
   if (!axis) {
     if (precision !== undefined) {
       value = value.toPrecision(precision);
       value = parseFloat(value).toString(); // no insignificant zeros
     }
 
-    if (options.round !== undefined) {
-      if (options.round < 0) {
-        let num = Math.pow(10, -1 * options.round);
+    if (round !== undefined) {
+      if (round < 0) {
+        let num = Math.pow(10, -1 * round);
         value = parseInt((1.0 * value / num).toFixed(0)) * num;
       } else {
-        value = parseFloat(value.toFixed(options.round));
+        value = parseFloat(value.toFixed(round));
       }
     }
   }