---
title: Custom Previews for File Upload Questions
product: Form Library
description: With SurveyJS form builder tool, you can create custom file previews for File Upload questions. This free demo for JavaScript offers a step-by-step guide on how to override the built-in preview functionality by adjusting the showPreview property and how to render personalized previews using the onAfterRenderQuestion event handler. 
framework: Angular
source: https://surveyjs.io/form-library/examples/custom-file-previews/angular
index: https://surveyjs.io/form-library/examples/overview.md
---

# Custom Previews for File Upload Questions (Angular)

SurveyJS File Upload questions support the file preview functionality out of the box (see the [File Upload](/form-library/examples/file-upload/) demo). This example demonstrates how you can override this functionality and implement custom file previews if required.

To implement custom file previews, follow the steps below:

1. Disable built-in file previews.      
Set the File Upload question's [`showPreview`](/form-library/documentation/api-reference/file-model#showPreview) property to `false`.

1. Implement a custom file preview component.       
In this demo, a custom component adds a `<div>` element to the bottom of the question. When users select one or multiple files for upload, this `<div>` displays "Download file" and "Remove file" buttons per uploaded file.

1. Register your custom component under the `sv-file-preview` name.      
    In HTML/CSS/JavaScript projects, register the component in `ReactElementFactory` as shown in the `index.js` file.           
    In React, register the component in `ReactElementFactory` as shown in the `FilePreviewComponent.jsx` file.          
    In Angular, register the component in `AngularComponentFactory` as shown in the `file-preview.component.ts` file.              
    In Vue.js, register the component in `ComponentFactory` as shown in the `main.ts` file.

> In this demo, files are uploaded to SurveyJS servers from where they are then deleted after a predefined period of time. We strongly encourage you to use your own servers for file uploads when you use SurveyJS to collect sensitive respondent data in your application.

## Files

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

```ts
export const json = {
  "elements": [
    {
      "type": "file",
      "title": "Please upload your files",
      "name": "files",
      "storeDataAsText": false,
      "allowMultiple": true,
      "showPreview": false,
      "maxSize": 102400
    }
  ]
};
```

### `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/file-preview.component.css`

```css
.my-preview-container {
    margin-top: 2em;
    max-width: calc(100% - 64px);
    margin-bottom: 1em;
    padding-left: 1em;
    padding-right: 1em;
    box-sizing: border-box;
    position: absolute;
    left: 50%;
    transform: translateX(-50%);
    bottom: 0;
}

.btn {
    appearance: none;
    border: 1px solid lightgray;
    cursor: pointer;
    padding: 4px 8px;
    color: var(--sjs2-color-fg-brand-on-primary, #fff);
    font-weight: 600;
    white-space: nowrap;
    text-overflow: ellipsis;
}

.button-container {
    width: 100%;
    display: flex;
    gap: 8px;
}

.btn--choose {
    background-color: var(--sjs2-color-project-brand-600, #19b394);
    overflow: hidden;
    flex: 1 1 auto;
}

.btn--choose:hover {
    background-color: var(--sjs2-color-bg-brand-primary-dim, rgb(20, 164, 139));
}

.btn--remove {
    background-color: var(--sjs2-color-bg-alert-primary, #e60a3e);
}

.btn--remove:hover {
    background-color: rgb(217, 4, 49);
}
```

### `src/app/components/file-preview.component.html`

```html
<div class="my-preview-container">
    <div class="files-container">
        <div class="button-container" *ngFor="let fileItem of question.value">
            <div class="btn btn--choose" (click)="downloadFile(fileItem)">
                {{"Download " + fileItem.name}}
            </div>
            <div class="btn btn--remove"
                 [class.disabled]="isReadOnly"
                 (click)="!isReadOnly && question.removeFile(fileItem.name)"
                 [attr.title]="isReadOnly ? 'Read-only mode' : 'Remove file'"
                 [style.cursor]="isReadOnly ? 'not-allowed' : 'pointer'"
                 [style.opacity]="isReadOnly ? 0.5 : 1">
                {{"X"}}
            </div>
        </div>
    </div>
</div>
```

### `src/app/components/file-preview.component.ts`

```ts
import { Component, Input } from "@angular/core";
import { QuestionFileModel } from "survey-core";

@Component({
    selector: "sv-file-custom-preview",
    templateUrl: "./file-preview.component.html",
    styleUrls: ["./file-preview.component.css"]
})
export class FilePreviewComponent {
    @Input() question!: QuestionFileModel;

    get isReadOnly(): boolean {
        return this.question.isReadOnly || (this.question.survey && this.question.survey.readOnly);
    }

    public downloadFile(fileItem: any) {
        fetch(fileItem.content)
            .then((response) => response.blob())
            .then((blob) => {
                const file = new File([blob], fileItem.name, {
                    type: fileItem.type
                });
                const reader = new FileReader();
                reader.onload = (e) => {
                    const a = document.createElement("a");
                    a.href = <string>e.target?.result;
                    a.download = fileItem.name;
                    a.click();
                };
                reader.readAsDataURL(file);
            })
            .catch((error) => {
                console.error("Error:", error);
            });
    }
}
```

### `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";
import { FilePreviewComponent } from "./file-preview.component";
import { AngularComponentFactory } from "survey-angular-ui";

AngularComponentFactory.Instance.registerComponent("sv-file-preview", FilePreviewComponent);

@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.onUploadFiles.add((_, options) => {
            const formData = new FormData();
            options.files.forEach((file) => {
                formData.append(file.name, file);
            });
        
            fetch("https://api.surveyjs.io/private/Surveys/uploadTempFiles", {
                method: "POST",
                body: formData
            })
                .then((response) => response.json())
                .then((data) => {
                    options.callback(
                        options.files.map((file) => {
                            return {
                                file: file,
                                content: "https://api.surveyjs.io/private/Surveys/getTempFile?name=" + data[file.name]
                            };
                        })
                    );
                })
                .catch((error) => {
                    console.error("Error: ", error);
                    options.callback([], [ "An error occurred during file upload." ]);
                });
        });
        async function deleteFile(fileURL) {
            try {
                const name = fileURL.split("=")[1];
                const apiUrl = `https://api.surveyjs.io/private/Surveys/deleteTempFile?name=${name}`;
                const response = await fetch(apiUrl, { method: "DELETE" });
        
                if (response.status === 200) {
                    console.log(`File ${name} was deleted successfully`);
                    return "success";
                } else {
                    console.error(`Failed to delete file: ${name}`);
                    return "error";
                }
            } catch (error) {
                console.error("Error while deleting file: ", error);
                return "error";
            }
        }
        
        survey.onClearFiles.add(async (_, options) => {
            if (!options.value || options.value.length === 0) {
                return options.callback("success");
            }
        
            const filesToDelete = options.fileName
                ? options.value.filter((item) => item.name === options.fileName)
                : options.value;
        
            if (filesToDelete.length === 0) {
                console.error(`File with name ${options.fileName} is not found`);
                return options.callback("error");
            }
        
            const results = await Promise.all(
                filesToDelete.map((file) => deleteFile(file.content))
            );
        
            if (results.every((res) => res === "success")) {
                options.callback("success");
            } else {
                options.callback("error");
            }
        });
        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";
import { FilePreviewComponent } from "./components/file-preview.component";

@NgModule({
    declarations: [AppComponent, SurveyComponent, FilePreviewComponent],
    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/custom-file-previews/reactjs.md)
- [Vue 3](https://surveyjs.io/form-library/examples/custom-file-previews/vue3js.md)
- [jQuery](https://surveyjs.io/form-library/examples/custom-file-previews/jquery.md)
- [Vanilla JS](https://surveyjs.io/form-library/examples/custom-file-previews/vanillajs.md)