How to load external scripts dynamically in Angular?

You can use following technique to dynamically load JS scripts and libraries on demand in your Angular project.

script.store.ts will contain the path of the script either locally or on a remote server and a name that will be used to load the script dynamically

 interface Scripts {
    name: string;
    src: string;
}  
export const ScriptStore: Scripts[] = [
    {name: 'filepicker', src: 'https://api.filestackapi.com/filestack.js'},
    {name: 'rangeSlider', src: '../../../assets/js/ion.rangeSlider.min.js'}
];

script.service.ts is an injectable service that will handle the loading of script, copy script.service.ts as it is

import {Injectable} from "@angular/core";
import {ScriptStore} from "./script.store";

declare var document: any;

@Injectable()
export class ScriptService {

private scripts: any = {};

constructor() {
    ScriptStore.forEach((script: any) => {
        this.scripts[script.name] = {
            loaded: false,
            src: script.src
        };
    });
}

load(...scripts: string[]) {
    var promises: any[] = [];
    scripts.forEach((script) => promises.push(this.loadScript(script)));
    return Promise.all(promises);
}

loadScript(name: string) {
    return new Promise((resolve, reject) => {
        //resolve if already loaded
        if (this.scripts[name].loaded) {
            resolve({script: name, loaded: true, status: 'Already Loaded'});
        }
        else {
            //load script
            let script = document.createElement('script');
            script.type = 'text/javascript';
            script.src = this.scripts[name].src;
            if (script.readyState) {  //IE
                script.onreadystatechange = () => {
                    if (script.readyState === "loaded" || script.readyState === "complete") {
                        script.onreadystatechange = null;
                        this.scripts[name].loaded = true;
                        resolve({script: name, loaded: true, status: 'Loaded'});
                    }
                };
            } else {  //Others
                script.onload = () => {
                    this.scripts[name].loaded = true;
                    resolve({script: name, loaded: true, status: 'Loaded'});
                };
            }
            script.onerror = (error: any) => resolve({script: name, loaded: false, status: 'Loaded'});
            document.getElementsByTagName('head')[0].appendChild(script);
        }
    });
}

}

Inject this ScriptService wherever you need it and load js libs like this

this.script.load('filepicker', 'rangeSlider').then(data => {
    console.log('script loaded ', data);
}).catch(error => console.log(error));

Yet another option would be to utilize scriptjs package for that matter which

allows you to load script resources on-demand from any URL

Example

Install the package:

npm i scriptjs

and type definitions for scriptjs:

npm install --save @types/scriptjs

Then import $script.get() method:

import { get } from 'scriptjs';

and finally load script resource, in our case Google Maps library:

export class AppComponent implements OnInit {
  ngOnInit() {
    get("https://maps.googleapis.com/maps/api/js?key=", () => {
        //Google Maps library has been loaded...
    });
  }
}

Demo

If you're using system.js, you can use System.import() at runtime:

export class MyAppComponent {
  constructor(){
    System.import('path/to/your/module').then(refToLoadedModule => {
      refToLoadedModule.someFunction();
    }
  );
}

If you're using webpack, you can take full advantage of its robust code splitting support with require.ensure :

export class MyAppComponent {
  constructor() {
     require.ensure(['path/to/your/module'], require => {
        let yourModule = require('path/to/your/module');
        yourModule.someFunction();
     }); 
  }
}

This might work. This Code dynamically appends the <script> tag to the head of the html file on button clicked.

const url = 'http://iknow.com/this/does/not/work/either/file.js';

export class MyAppComponent {
    loadAPI: Promise<any>;

    public buttonClicked() {
        this.loadAPI = new Promise((resolve) => {
            console.log('resolving promise...');
            this.loadScript();
        });
    }

    public loadScript() {
        console.log('preparing to load...')
        let node = document.createElement('script');
        node.src = url;
        node.type = 'text/javascript';
        node.async = true;
        node.charset = 'utf-8';
        document.getElementsByTagName('head')[0].appendChild(node);
    }
}