fix(data-labels-style): fixed serializations of DataLabels.Style.Colors

docs/BlazorApexCharts.Docs/Components/ChartTypes/HeatmapCharts/DataLabelColors.razor

@@ -0,0 +1,48 @@
+<DemoContainer>
+	<ApexChart TItem="SupportIncident"
+			   Title="Incident Severity"
+			   Options="options">
+
+		@foreach (var source in incidents.GroupBy(e => e.Source).OrderBy(e => e.Key))
+		{
+			<ApexPointSeries TItem="SupportIncident"
+							 Items="source.OrderBy(e=>e.WeekNumber)"
+							 Name="@source.Key.ToString()"
+							 SeriesType="SeriesType.Heatmap"
+							 Color="@GetColor(source.Key)"
+							 ShowDataLabels="true"
+							 XValue="@(e => e.WeekName)"
+							 YAggregate="@(e => (int)e.Average(a=>a.Severity))" />
+		}
+
+	</ApexChart>
+</DemoContainer>
+
+@code {
+	private List<SupportIncident> incidents { get; set; } = SampleData.GetSupportIncidents();
+	private ApexChartOptions<SupportIncident> options = new ApexChartOptions<SupportIncident>
+	{
+		DataLabels = new DataLabels
+		{
+			Style = new DataLabelsStyle
+			{
+				Colors = ["function(opts) { return (opts.series[opts.seriesIndex][opts.dataPointIndex] < 30) ? '#00f' : '#f00'; }"],
+			},
+		},
+	};
+
+	private string GetColor(IncidentSource source)
+	{
+		switch (source)
+		{
+			case IncidentSource.Internal:
+				return "#FF0000";
+			case IncidentSource.ThirdParty:
+				return "#0000FF";
+			case IncidentSource.Integration:
+				return "#FF00FF";
+			default:
+				return "#008FFB";
+		}
+	}
+}

docs/BlazorApexCharts.Docs/Components/ChartTypes/HeatmapCharts/HeatmapCharts.razor

@@ -20,6 +20,12 @@
         </Snippet>
     </CodeSnippet>
 
+    <CodeSnippet Title="Data Labels Colors" ClassName=@typeof(Colors).ToString()>
+        <Snippet>
+            <DataLabelColors />
+        </Snippet>
+    </CodeSnippet>
+
     <CodeSnippet Title=NoShade ClassName=@typeof(NoShade).ToString()>
         <Snippet>
             <NoShade />

src/Blazor-ApexCharts/Internal/ChartUtilities.cs

@@ -0,0 +1,65 @@
+using System;
+using System.Text.RegularExpressions;
+
+namespace ApexCharts.Internal;
+
+/// <summary>
+/// Provides JavaScript related helper utilities for ApexCharts internal processing.
+/// </summary>
+internal static class ChartUtilities
+{
+    /// <summary>
+    /// Regex that matches the beginning of a JavaScript function or arrow function (including optional leading comments).
+    /// </summary>
+    private static readonly Regex JsFunctionStartRegex = new(
+        @"^\s*(?:/\*[\s\S]*?\*/\s*|//[^\n]*\n\s*)*(?:async\s+)?(?:
+              function\b
+            | \([^)]*\)\s*=>          # (args) =>
+            | [A-Za-z_$][\w$]*\s*=>   # identifier =>
+        )",
+        RegexOptions.IgnoreCase | RegexOptions.Compiled | RegexOptions.CultureInvariant | RegexOptions.IgnorePatternWhitespace);
+
+    /// <summary>
+    /// Regex that matches immediately-invoked function expressions (IIFE) using the traditional function keyword.
+    /// </summary>
+    private static readonly Regex IifeFunctionRegex = new(
+        @"^\s*\(\s*(?:async\s+)?function\b",
+        RegexOptions.IgnoreCase | RegexOptions.Compiled | RegexOptions.CultureInvariant);
+
+    /// <summary>
+    /// Regex that matches immediately-invoked arrow function expressions.
+    /// </summary>
+    private static readonly Regex IifeArrowRegex = new(
+        @"^\s*\(\s*(?:async\s+)?\([^)]*\)\s*=>",
+        RegexOptions.IgnoreCase | RegexOptions.Compiled | RegexOptions.CultureInvariant);
+
+    /// <summary>
+    /// Determines whether the provided string appears to represent a JavaScript function
+    /// (standard function declaration, arrow function, or IIFE).
+    /// </summary>
+    /// <param name="candidate">The string to inspect.</param>
+    /// <returns>
+    /// <see langword="true"/> if the string structurally resembles a JavaScript function;
+    /// otherwise, <see langword="false"/>.
+    /// </returns>
+    internal static bool IsJavaScriptFunction(string candidate)
+    {
+        if (string.IsNullOrWhiteSpace(candidate))
+            return false;
+
+        // Quick cheap pre-filter: avoid regex if no plausible tokens
+        if (!(candidate.Contains("function", StringComparison.OrdinalIgnoreCase) ||
+              candidate.Contains("=>", StringComparison.Ordinal)))
+            return false;
+
+        // Direct structural check at start
+        if (JsFunctionStartRegex.IsMatch(candidate))
+            return true;
+
+        // IIFE patterns: (function(...) {...})(), (() => {...})(), etc.
+        if (IifeFunctionRegex.IsMatch(candidate) || IifeArrowRegex.IsMatch(candidate))
+            return true;
+
+        return false;
+    }
+}

src/Blazor-ApexCharts/Internal/Converters/ListStringOrFunctionConverter.cs

@@ -0,0 +1,71 @@
+using System;
+using System.Collections.Generic;
+using System.Text.Json;
+using System.Text.Json.Serialization;
+
+namespace ApexCharts.Internal;
+
+/// <summary>
+/// Converter for lists of strings that detects entries containing a JavaScript function definition
+/// (case-insensitive search for the word "function") and serializes those as an object with the "@eval" key
+/// so that ApexCharts interprets them as executable functions instead of plain strings.
+///
+/// Output behavior:
+/// - Normal strings are written as JSON string elements inside the array.
+/// - Strings representing functions are written as:
+///   { "@eval": "function(x) { return x; }" }
+///
+/// Example:
+/// C# input:
+/// <code>
+/// new List&lt;string&gt;
+/// {
+///     "Label 1",
+///     "function(w) { return w; }",
+///     "Another label"
+/// };
+/// </code>
+///
+/// JSON output:
+/// <code>
+/// [
+///   "Label 1",
+///   { "@eval": "function(w) { return w; }" },
+///   "Another label"
+/// ]
+/// </code>
+///
+/// Note: Deserialization (Read) is not implemented because this converter is intended only for outgoing
+/// serialization to the client.
+/// </summary>
+internal class ListStringOrFunctionConverter : JsonConverter<List<string>>
+{
+    public override bool CanConvert(Type typeToConvert) => typeToConvert == typeof(List<string>);
+
+    public override List<string> Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+    {
+        throw new NotImplementedException();
+    }
+
+    public override void Write(Utf8JsonWriter writer, List<string> value, JsonSerializerOptions options)
+    {
+        writer.WriteStartArray();
+
+        foreach (var item in value)
+        {
+            if (ChartUtilities.IsJavaScriptFunction(item))
+            {
+                writer.WriteStartObject();
+                writer.WritePropertyName("@eval");
+                JsonSerializer.Serialize(writer, item, options);
+                writer.WriteEndObject();
+            }
+            else
+            {
+                writer.WriteStringValue(item);
+            }
+        }
+
+        writer.WriteEndArray();
+    }
+}

src/Blazor-ApexCharts/Models/ApexChartOptions.cs

@@ -1856,8 +1856,36 @@ public class DataLabelsBackground
     public class DataLabelsStyle
     {
         /// <summary>
-        /// Fore colors for the dataLabels. Accepts an array of string colors (['#333', '#999']) or an array of functions ([function(opts) { return '#333' }]) (Each index in the array corresponds to the series).
+        /// Fore colors for the dataLabels (each index in the array corresponds to the series).
         /// </summary>
+        /// <remarks>
+        /// Accepts:
+        /// <list type="bullet">
+        /// <item><description>An array of string colors (e.g. <c>{ "#333", "#999" }</c>)</description></item>
+        /// <item><description>An array of JavaScript functions serialized as strings (e.g. <c>{ "function(opts) { return '#333' }" }</c>)</description></item>
+        /// </list>
+        /// Each index in the array corresponds to the series index.
+        /// <para>Examples:</para>
+        /// <code>
+        /// // Using static colors
+        /// var style = new DataLabelsStyle
+        /// {
+        ///     Colors = new List&lt;string&gt; { "#333", "#999" }
+        /// };
+        ///
+        /// // Using JavaScript functions (strings will be passed through the converter)
+        /// var styleWithFunctions = new DataLabelsStyle
+        /// {
+        ///     Colors = new List&lt;string&gt;
+        ///     {
+        ///         "function(opts) { return '#333'; }",
+        ///         "function(opts) { return opts.seriesIndex % 2 ? '#999' : '#555'; }"
+        ///     }
+        /// };
+        /// </code>
+        /// For short inline snippets use the inline code tag, e.g. <c>"#333"</c>.
+        /// </remarks>
+        [JsonConverter(typeof(ListStringOrFunctionConverter))]
         public List<string> Colors { get; set; }
 
         /// <summary>