---
title: Simplify Cascade Conditions
product: Form Library
description: You can implement skip logic and branching for your surveys. Based on the response to the current question, one or more questions down the line may be either hidden or shown. View a free demo example for JavaScript to learn more.
framework: Angular
source: https://surveyjs.io/form-library/examples/conditional-logic-and-branching-in-surveys/angular
index: https://surveyjs.io/form-library/examples/overview.md
---

# Simplify Cascade Conditions (Angular)

In a cascade condition, a question's visibility depends on the previous question, whose visibility, in turn, depends on a question before it, and so on. Cascade conditions may result in lengthy Boolean expressions because each expression must include conditions from previous cascade levels. In this example, questions form the following multi-level cascade:

`"tradeIn"` → `"make"` → `"model"` → `"year"` → `"mileage"`

Each question after `"tradeIn"` depends on the answer given to the previous question. Typical conditional visibility expressions ([`visibleIf`](/form-library/documentation/api-reference/question#visibleIf)) in this case look as follows:

```js
{
  "elements": [{
    "name": "tradeIn",
    "title": "Do you have a vehicle to trade in?"
  }, {
    "name": "make",
    "title": "Vehicle make",
    "visibleIf": "{tradeIn} = 'Yes'"
  }, {
    "name": "model",
    "title": "Vehicle model",
    "visibleIf": "{tradeIn} = 'Yes' and {make} notempty"
  }, {
    "name": "year",
    "title": "Model year",
    "visibleIf": "{tradeIn} = 'Yes' and {make} notempty and {model} notempty"
  }, {
    "name": "mileage",
    "title": "Approximate mileage (miles)",
    "visibleIf": "{tradeIn} = 'Yes' and {make} notempty and {model} notempty and {year} notempty"
  }]
}
```

As you can see, cascade conditions accumulate, and the `visibleIf` expressions for the lowest-level questions (`"year"`, `"mileage"`, etc.) include conditions of the higher-level questions.

To shorten expressions, you can set the [`clearInvisibleValues`](/form-library/documentation/api-reference/survey-data-model#clearInvisibleValues) property to `"onHidden"`. With this setting, expressions may take into account only the previous-level question. For example, the `"model"` question can use `visibleIf: "{make} notempty"` instead of repeating the `{tradeIn} = 'Yes'` condition from the previous level.

Without `clearInvisibleValues` set to `"onHidden"`, hidden questions retain their values. If you used shorter expressions in this case, a change in a higher-level question wouldn't propagate down the cascade, and lowest-level questions would remain visible even though questions upon which they depend were hidden.

To see the abbreviated `visibleIf` expressions, view the survey JSON schema in the **Code** tab.

Note that this simplification also slightly changes the behavior. If a question had a value before hiding, this value will not reappear when the question becomes visible again. If this is not the desired behavior, we recommend using lengthy expressions.

## Files

### `src/app/components/json.ts`

```ts
export const json = {
  "clearInvisibleValues": "onHidden",
  "elements": [
    {
      "type": "radiogroup",
      "name": "tradeIn",
      "title": "Do you have a vehicle to trade in?",
      "isRequired": true,
      "choices": [ "Yes", "No" ],
      "colCount": 0
    },
    {
      "type": "dropdown",
      "name": "make",
      "title": "Vehicle make",
      "visibleIf": "{tradeIn} = 'Yes'",
      "isRequired": true,
      "choices": [ "Toyota", "Honda", "Ford", "Chevrolet", "BMW", "Mercedes-Benz", "Other" ]
    },
    {
      "type": "text",
      "name": "model",
      "title": "Vehicle model",
      "visibleIf": "{make} notempty",
      "isRequired": true
    },
    {
      "type": "dropdown",
      "name": "year",
      "title": "Model year",
      "visibleIf": "{model} notempty",
      "isRequired": true,
      "choicesMin": 1990,
      "choicesMax": 2026
    },
    {
      "type": "text",
      "name": "mileage",
      "title": "Approximate mileage (miles)",
      "visibleIf": "{year} notempty",
      "inputType": "number",
      "isRequired": true
    }
  ]
}
;
```

### `src/app/components/survey.component.css`

```css
/* You can add your custom CSS here. */
```

### `src/app/components/survey.component.html`

```html
<survey [model]="model" style="position: absolute; top: 0; left: 0; right: 0; bottom: 0; height:100%"></survey>
```

### `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
<component-survey></component-survey>
```

### `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
<app-root></app-root>
```

### `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/conditional-logic-and-branching-in-surveys/reactjs.md)
- [Vue 3](https://surveyjs.io/form-library/examples/conditional-logic-and-branching-in-surveys/vue3js.md)
- [jQuery](https://surveyjs.io/form-library/examples/conditional-logic-and-branching-in-surveys/jquery.md)
- [Vanilla JS](https://surveyjs.io/form-library/examples/conditional-logic-and-branching-in-surveys/vanillajs.md)