Create custom condition/expression properties


Survey.Serializer.addProperty("matrix", { name: "showHeaderIf:condition", category: "logic",
   onExecuteExpression: (obj, res) => { obj.showHeader = res === true; }

                    var json = {
  "elements": [
      "type": "checkbox",
      "name": "car",
      "title": "What cars have you being drived?",
      "isRequired": true,
      "colCount": 3,
      "choices": [
      "type": "matrix",
      "name": "carRating",
      "isRequired": true,
      "visibleIf": "{car.length} > 0",
      "showHeaderIf": "{car.length} > 1",
      "title": "Please select best car for each category?",
      "rowsVisibleIf": "{car} contains {item}",
      "isAllRowRequired": true,
      "columns": [
      "rows": [

                    window.survey = new Survey.Model(json);
            survey.onComplete.add(function(sender) {
            document.querySelector('#surveyResult').textContent =
            "Result JSON:\n" + JSON.stringify(, null, 3);
                ko.applyBindings({ model: survey }, document.getElementById("surveyElement"));

<!DOCTYPE html>
<html lang="en">
    <title>Create custom condition/expression properties, Knockoutjs Survey Library Example</title>
<meta name="viewport" content="width=device-width" />
    <script src=""></script>
    <script src="/DevBuilds/survey-core/survey.core.min.js"></script>
    <script src="/DevBuilds/survey-core/survey.i18n.min.js"></script>
    <script src="/DevBuilds/survey-knockout-ui/survey-knockout-ui.min.js"></script>
    <link href="/DevBuilds/survey-core/defaultV2.min.css" type="text/css" rel="stylesheet" />
    <link rel="stylesheet" href="./index.css">

<body style="margin: 0">
            <div id="surveyElement" style="display:inline-block;width:100%;">
                    <survey params="survey: model"></survey>
    <div id="surveyResult"></div>

<script type="text/javascript" src="./index.js"></script>

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