---
title: Loop and Merge: Nested Loops
product: Form Library
description: Learn how to build nested loops in a form using Dynamic Panels and Dynamic Matrices. This JavaScript form builder demo shows how to create nested repeating question sets and display one input field per page.
framework: Angular
source: https://surveyjs.io/form-library/examples/nested-loops/angular
index: https://surveyjs.io/form-library/examples/overview.md
---
# Loop and Merge: Nested Loops (Angular)
SurveyJS Form Library supports nested loops through its Loop and Merge functionality. In a nested loop setup, an outer loop iterates over a primary list of items, while an inner loop handles a related set of sub-items. For example, the form below asks an organization owner to provide information about departments (outer loop) and the employees within each department (inner loop).
To implement a nested loop, use a [Dynamic Panel](/form-library/documentation/api-reference/dynamic-panel-model) as the outer loop and nest either another Dynamic Panel or a [Dynamic Matrix](/form-library/documentation/api-reference/dynamic-matrix-table-question-model) inside it. For a Dynamic Panel, define the repeated questions using the [`templateElements`](/form-library/documentation/api-reference/dynamic-panel-model#templateElements) property. For a nested Dynamic Matrix, configure the repeated fields using the [`columns`](/form-library/documentation/api-reference/dynamic-matrix-table-question-model#columns) property.
Each loop iteration displays a title. To customize titles in a Dynamic Panel, use the [`templateTitle`](/form-library/documentation/api-reference/dynamic-panel-model#templateTitle) property. For a Dynamic Matrix, use [`singleInputTitleTemplate`](/form-library/documentation/api-reference/matrix-table-with-dropdown-list#singleInputTitleTemplate). Both properties support dynamic placeholders and text piping from other questions and loop levels.
Nested loops can be enabled only if your survey displays one input field per page. To enable this structure, set the [`questionsOnPageMode`](/form-library/documentation/api-reference/survey-data-model#questionsOnPageMode) property to `"inputPerPage"` at the survey level.
## Files
### `src/app/components/json.ts`
```ts
export const json = {
"questionsOnPageMode": "inputPerPage",
"pages": [
{
"name": "page1",
"elements": [
{
"type": "paneldynamic",
"name": "departments",
"title": "List all departments in your company and their employees",
"templateElements": [
{
"type": "text",
"name": "department",
"title": "Department name",
"defaultDisplayValue": "[not set]",
"isRequired": true
},
{
"type": "matrixdynamic",
"name": "employees",
"title": "Add employees to the department",
"columns": [
{
"name": "employee-name",
"title": "Name",
"cellType": "text",
"isRequired": true,
"defaultDisplayValue": "[not set]"
},
{
"name": "employment-date",
"title": "Employment date",
"cellType": "text",
"inputType": "date"
}
],
"singleInputTitleTemplate": "Employee: {row.employee-name}",
"rowCount": 0,
"addRowText": "Add Employee",
"removeRowText": "Remove Employee"
}
],
"templateTitle": "Department: {panel.department}",
"panelCount": 1,
"addPanelText": "Add Department"
}
]
}
]
};
```
### `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/nested-loops/reactjs.md)
- [Vue 3](https://surveyjs.io/form-library/examples/nested-loops/vue3js.md)
- [jQuery](https://surveyjs.io/form-library/examples/nested-loops/jquery.md)
- [Vanilla JS](https://surveyjs.io/form-library/examples/nested-loops/vanillajs.md)