--- title: Expressions in Dynamic Panel product: Form Library description: Dynamic panels let you add a duplicate panel in order to continue a list of answers. View this free example for JavaScript to learn how to use expressions in such panels and calculate entered values on the fly. framework: Angular source: https://surveyjs.io/form-library/examples/how-to-use-expressions-in-dynamic-panel/angular index: https://surveyjs.io/form-library/examples/overview.md --- # Expressions in Dynamic Panel (Angular) Expressions let you configure conditional logic to create dynamic surveys. You can use expressions to implement branching and skip logic, dynamically show and hide questions, mark them as required, enable and disable them, and perform calculations right in the survey JSON schema. This example demonstrates expressions in a [Dynamic Panel](/form-library/documentation/api-reference/dynamic-panel-model). Here expressions are used to calculate employment duration. Enter a company name and employment dates to see the number of days employed for this company. You can add as many companies as you want—days employed will be added up and displayed under the Dynamic Panel. ## Access Questions Within a Panel To reference questions within the same panel in your expressions, use the `panel` prefix as follows: `{panel.questionName}`. Refer to the expressions within the Employment History panel for code examples. ## Dynamically Calculate Values Expressions support built-in functions and allow you to create custom functions for in-survey calculations. In this demo, expressions calculate the number of days employed using built-in [`diffDays`](https://surveyjs.io/form-library/documentation/design-survey/conditional-logic#diffdays) and [`sumInArray`](https://surveyjs.io/form-library/documentation/design-survey/conditional-logic#suminarray) functions. For more information on how to use these and other built-in functions or how to implement a custom function, refer to the [Expressions](https://surveyjs.io/form-library/documentation/design-survey/conditional-logic#expressions) help topic. ## Manage Question Visibility You can use expressions to implement conditional visibility for questions, choice options, matrix columns/rows, and other elements. In this demo, the number of days for individual companies is only displayed when you enter both the company name and employment dates. To implement this functionality, assign a Boolean expression to the [`visibleIf`](https://surveyjs.io/form-library/documentation/api-reference/question#visibleIf) property. You can find more details in the [Conditional Visibility](https://surveyjs.io/form-library/documentation/design-survey/conditional-logic#conditional-visibility) help topic. ## Validate Question Values Expressions can be used to add data validation to your survey. In this example, the Employment Dates question fields use the `minValueExpression` and `maxValueExpression` properties to ensure that the end date falls within the range between the selected start date and the current date. For more information about data validation in SurveyJS Form Library, refer to the following help topic: [Data Validation](https://surveyjs.io/form-library/documentation/data-validation). ## Files ### `src/app/components/json.ts` ```ts export const json = { "elements": [ { "type": "paneldynamic", "name": "employment-history", "title": "Employment History", "templateElements": [ { "type": "text", "name": "company", "title": "Company", "isRequired": true }, { "type": "multipletext", "name": "employment-dates", "title": "Employment dates", "items": [ { "name": "start", "isRequired": true, "inputType": "date", "title": "Start", "maxValueExpression": "today()" }, { "name": "end", "isRequired": true, "inputType": "date", "title": "End", "minValueExpression": "{panel.employment-dates.start}", "maxValueExpression": "today()" } ] }, { "type": "expression", "name": "days-employed", "title": "Days employed by {panel.company}:", "visibleIf": "{panel.company} notempty and {panel.employment-dates.start} notempty and {panel.employment-dates.end} notempty", "titleLocation": "left", "expression": "diffDays({panel.employment-dates.start}, {panel.employment-dates.end})" } ], "panelCount": 1, "addPanelText": "Add company" }, { "type": "expression", "name": "total-days-employed", "title": "Total days employed:", "titleLocation": "left", "expression": "sumInArray({employment-history}, 'days-employed')" } ], "checkErrorsMode": "onValueChanged" }; ``` ### `src/app/components/survey.component.css` ```css /* You can add your custom CSS here. */ ``` ### `src/app/components/survey.component.html` ```html ``` ### `src/app/components/survey.component.ts` ```ts import { Component, OnInit } from "@angular/core"; import { Model } from "survey-core"; import { json } from "./json"; import "./survey.component.css"; import "survey-core/survey-core.min.css"; @Component({ // tslint:disable-next-line:component-selector selector: "component-survey", templateUrl: "./survey.component.html", styleUrls: ["./survey.component.css"] }) export class SurveyComponent implements OnInit { model: Model; ngOnInit() { const survey = new Model(json); survey.onComplete.add((sender, options) => { console.log(JSON.stringify(sender.data, null, 3)); }); this.model = survey; } } ``` ### `src/app/components/theme.ts` ```ts export const themeJson = {}; ``` ### `src/app/app.component.css` ```css ``` ### `src/app/app.component.html` ```html ``` ### `src/app/app.component.ts` ```ts import { Component } from "@angular/core"; @Component({ selector: "app-root", templateUrl: "./app.component.html", styleUrls: ["./app.component.css"] }) export class AppComponent { title = "CodeSandbox"; } ``` ### `src/app/app.module.ts` ```ts import { BrowserModule } from "@angular/platform-browser"; import { NgModule } from "@angular/core"; import { AppComponent } from "./app.component"; import { SurveyModule } from "survey-angular-ui"; import { SurveyComponent } from "./components/survey.component"; @NgModule({ declarations: [AppComponent, SurveyComponent], imports: [BrowserModule, SurveyModule], providers: [], bootstrap: [AppComponent] }) export class AppModule { } ``` ### `src/environments/environment.prod.ts` ```ts export const environment = { production: true }; ``` ### `src/environments/environment.ts` ```ts // The file contents for the current environment will overwrite these during build. // The build system defaults to the dev environment which uses `environment.ts`, but if you do // `ng build --env=prod` then `environment.prod.ts` will be used instead. // The list of which env maps to which file can be found in `.angular-cli.json`. export const environment = { production: false }; ``` ### `src/index.html` ```html ``` ### `src/main.ts` ```ts import { enableProdMode } from "@angular/core"; import { platformBrowserDynamic } from "@angular/platform-browser-dynamic"; import { AppModule } from "./app/app.module"; import { environment } from "./environments/environment"; if (environment.production) { enableProdMode(); } platformBrowserDynamic() .bootstrapModule(AppModule) .catch(err => console.log(err)); ``` ### `src/polyfills.ts` ```ts /** * This file includes polyfills needed by Angular and is loaded before the app. * You can add your own extra polyfills to this file. * * This file is divided into 2 sections: * 1. Browser polyfills. These are applied before loading ZoneJS and are sorted by browsers. * 2. Application imports. Files imported after ZoneJS that should be loaded before your main * file. * * The current setup is for so-called "evergreen" browsers; the last versions of browsers that * automatically update themselves. This includes Safari >= 10, Chrome >= 55 (including Opera), * Edge >= 13 on the desktop, and iOS 10 and Chrome on mobile. * * Learn more in https://angular.io/docs/ts/latest/guide/browser-support.html */ /*************************************************************************************************** * BROWSER POLYFILLS */ /** IE9, IE10 and IE11 requires all of the following polyfills. **/ // import 'core-js/es6/symbol'; // import 'core-js/es6/object'; // import 'core-js/es6/function'; // import 'core-js/es6/parse-int'; // import 'core-js/es6/parse-float'; // import 'core-js/es6/number'; // import 'core-js/es6/math'; // import 'core-js/es6/string'; // import 'core-js/es6/date'; // import 'core-js/es6/array'; // import 'core-js/es6/regexp'; // import 'core-js/es6/map'; // import 'core-js/es6/weak-map'; // import 'core-js/es6/set'; /** IE10 and IE11 requires the following for NgClass support on SVG elements */ // import 'classlist.js'; // Run `npm install classlist.js`. /** IE10 and IE11 requires the following for the Reflect API. */ // import 'core-js/es6/reflect'; /** Evergreen browsers require these. **/ // Used for reflect-metadata in JIT. If you use AOT (and only Angular decorators), you can remove. import "core-js/proposals/reflect-metadata"; /** * Required to support Web Animations `@angular/platform-browser/animations`. * Needed for: All but Chrome, Firefox and Opera. http://caniuse.com/#feat=web-animation **/ // import 'web-animations-js'; // Run `npm install web-animations-js`. /*************************************************************************************************** * Zone JS is required by default for Angular itself. */ import "zone.js/dist/zone"; // Included with Angular CLI. /*************************************************************************************************** * APPLICATION IMPORTS */ ``` ### `src/styles.css` ```css /* You can add your custom CSS here. */ ``` ### `src/typings.d.ts` ```ts /* SystemJS module definition */ declare var module: NodeModule; interface NodeModule { id: string; } ``` ### `.angular-cli.json` ```json { "apps": [ { "root": "src", "outDir": "dist", "assets": [ "assets", "favicon.ico" ], "index": "index.html", "main": "main.ts", "polyfills": "polyfills.ts", "prefix": "app", "styles": [ "styles.css" ], "scripts": [ ], "environmentSource": "environments/environment.ts", "environments": { "dev": "environments/environment.ts", "prod": "environments/environment.prod.ts" } } ] } ``` ### `_tsconfig.json` ```json { "compileOnSave": false, "compilerOptions": { "baseUrl": "./", "outDir": "./dist/out-tsc", "sourceMap": true, "declaration": false, "allowSyntheticDefaultImports": true, "downlevelIteration": true, "experimentalDecorators": true, "moduleResolution": "node", "importHelpers": true, "resolveJsonModule": true, "target": "es2015", "module": "es2020", "lib": [ "es2018", "dom" ] } } ``` ### `package.json` ```json { "name": "surveyjs-angular", "scripts": { "ng": "ng", "start": "ng serve", "build": "ng build --prod", "test": "ng test", "lint": "ng lint", "e2e": "ng e2e" }, "private": true, "dependencies": { "@angular/animations": "14.1.1", "@angular/cdk": "14.1.1", "@angular/common": "14.1.1", "@angular/compiler": "14.1.1", "@angular/core": "14.1.1", "@angular/forms": "14.1.1", "@angular/platform-browser": "14.1.1", "@angular/platform-browser-dynamic": "14.1.1", "@angular/router": "14.1.1", "core-js": "3.6.4", "rxjs": "6.5.4", "survey-core": "latest", "survey-angular-ui": "latest", "tslib": "1.13.0", "zone.js": "0.11.7" }, "devDependencies": { "@angular/cli": "1.6.6", "@angular/compiler-cli": "^5.2.0", "@angular/language-service": "^5.2.0", "@types/core-js": "0.9.46", "@types/jasmine": "~2.8.3", "@types/jasminewd2": "~2.0.2", "@types/node": "~6.0.60", "codelyzer": "^4.0.1", "jasmine-core": "~2.8.0", "jasmine-spec-reporter": "~4.2.1", "karma": "~2.0.0", "karma-chrome-launcher": "~2.2.0", "karma-coverage-istanbul-reporter": "^1.2.1", "karma-jasmine": "~1.1.0", "karma-jasmine-html-reporter": "^0.2.2", "protractor": "~5.1.2", "ts-node": "~4.1.0", "tslint": "~5.9.1", "typescript": "3.9.7" }, "keywords": [ "angular", "surveyjs" ], "description": "SurveyJS-Angular example project" } ``` ## Other Frameworks - [React](https://surveyjs.io/form-library/examples/how-to-use-expressions-in-dynamic-panel/reactjs.md) - [Vue 3](https://surveyjs.io/form-library/examples/how-to-use-expressions-in-dynamic-panel/vue3js.md) - [jQuery](https://surveyjs.io/form-library/examples/how-to-use-expressions-in-dynamic-panel/jquery.md) - [Vanilla JS](https://surveyjs.io/form-library/examples/how-to-use-expressions-in-dynamic-panel/vanillajs.md)