I would like to use Plupload in an Angular2 component and access the Plupload JavaScript file from a CDN. I want it specific to a component so that it is not downloaded if it is not required - I want it to be in a lazy loaded module. How can I do this?
Now fully answered on this page!
The result of this quest, which included offering and awarding bounties to two people who worked hard with me on it, is as follows:
How to use a lazy loaded script in Angular 2
(See edit history for the ugly details that used to make up this question.)
Here's the overview of what you need to do to create a lazy-loaded Plupload feature while loading Plupload from a CDN:
<script>
tag to the page to load the Plupload library from a CDN."plupload is undefined"
error).Complete, working code: https://plnkr.co/edit/4t39Rod4YNAOrHmZdxqc?p=preview
Please take note of the following points in my implementation:
plupload
variable. As long as window.plupload
does not exist, it means the library hasn't been loaded yet and that we should NOT proceed. For simplicity my code just waits for one second and proceeds.document.getElementById('filelist')
). This is something Angular discourages and that you should try avoiding whenever possible. More specifically direct DOM access is used in the following places:
browse_button
config option). For this I could not avoid the direct DOM reference and I used the @ViewChild
decorator to get a hold of the "Select Files" button.fileList
which I display in the template using a standard *ngFor
.Let me know if you have any questions.
In this approach no need for any extra loader modules.
See example (check console for Woohoo): http://plnkr.co/edit/gfUs4Uhe8kMGzPxwpBay?p=preview updated plunker: https://plnkr.co/edit/leG062tg7uX8sLrA0i2i?p=preview
You can lazyload some js by adding the script url to you document:
Create a my-lazy-load.function.ts
:
export function lazyload(url) {
// based on https://friendlybit.com/js/lazy-loading-asyncronous-javascript/
let scripts = document.getElementsByTagName('script');
for (let i = scripts.length; i--;) {
if (scripts[i].src.match(url)) return true;
}
let s = document.createElement('script');
s.type = 'text/javascript';
s.async = true;
s.src = url;
let x = document.getElementsByTagName('script')[0];
x.parentNode.insertBefore(s, x);
return true;
}
In your component that you want to add plupload:
import {lazyload} from "./my-lazy-load.function.ts";
export class MyComponent implements OnInit {
pluploadInterval:number = null;
hasPlupload: boolean = false;
ngOnInit() {
lazyload("https://cdnjs.cloudflare.com/ajax/libs/plupload/2.3.1/plupload.full.min.js");
this.pluploadInterval = window.setInterval(()=>{
if(window.plupload) { // you can check existence of plupload object any way you want
// Woohoo, I am ready to be used
this.hasPlupload = true; // everything is run outside ngZone, wrap it if angular2 is not reacting to changes, or change window.setInterval to setInterval
window.clearInterval(this.pluploadInterval); // don't forget to clean interval
}
}, 100); // timeinterval can vary
....
The browser will load this automatically.
Notice if(plupload)
it assumes that there is global object plupload that the script adds (I do not know if it truely added, check your working example in pure javascript). As it is jquery extension you can check it's prototype like this: jQuery test for whether an object has a method?
OLD HISTORICAL:
@Reid here is plunker: https://plnkr.co/edit/zDWWQbTQUSHBqCsrUMUi?p=preview the plupload is actually loaded, but added to require with define("plupload", ['./moxie'], extract);
I am not sure at the moment how to extract from there and which package require is belong to... the code for finding correct module loader belongs to plupload itself, here it is (from plupload.dev.js):
if (typeof define === "function" && define.amd) {
define("plupload", ['./moxie'], extract);
} else if (typeof module === "object" && module.exports) {
module.exports = extract(require('./moxie'));
} else {
global.plupload = extract(global.moxie);
}
I think that your best bet is to use the Require.js Library so that you can dynamically load your scripts from within your components.
The small trade off is that you will have to add this 18KB library to your index.html page (CDN), however this could save you huge amounts of loading if your 3rd party libraries are massive.
I have no experience with using plupload, so instead I put together the following plunkr which uses an external animation library, drawn from a CDN. The plunkr animates a number from 0 - 100.
https://plnkr.co/edit/fJCtezsERYHOYplLh7Jo?p=preview
<script src="https://cdnjs.cloudflare.com/ajax/libs/require.js/2.3.3/require.min.js"></script>
component.ts
ngOnInit(){
// Dynamically loads the framework from the CDN.
require(["https://cdnjs.cloudflare.com/ajax/libs/gsap/1.19.1/TweenLite.min.js"],
// This function is then called ONCE LOAD IS COMPLETE
function (common) {
// Do greensock things
var demo = {score:0},
scoreDisplay = document.getElementById("scoreDisplay");
//create a tween that changes the value of the score property of the demo object from 0 to 100 over the course of 20 seconds.
var tween = TweenLite.to(demo, 20, {score:100, onUpdate:showScore})
//each time the tween updates this function will be called.
function showScore() {
scoreDisplay.innerHTML = demo.score.toFixed(2);
}
});
}
What I like about this approach, is that in the onLoad callback from require
, the syntax is unchanged from a normal implementation of the library, so you can just copy paste your currently working code into the callback.
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