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resl (RESource Loader) is a tiny streaming asset loader intended for use with WebGL applications.
// Here we call resl and tell it to start preloading resourcesrequire('resl')({// A call to resl takes a JSON object as configuration.// The configuration object must contain a manifest field which specifies// a list of all resources to load and their types.manifest:{// Each entry in the manifest represents an asset to be loaded'scores':{type:'text',// the type declares the type of the assetsrc:'data/scores.csv'// and src declares the URL of the asset},// You can also specify HTML elements as assets'an_image':{type:'image',src:'images/some-image.png'},// Assets can also be streamed as well'some_video':{type:'video',stream:true,// setting the streaming flag specifies that// the done() callback will fire as soon as the// asset has started loadingsrc:'videos/some-video.mp4'},// You can also specify custom parsers for your assets'json_data':{type:'text',src:'mydata.json',parser:JSON.parse// Here we call JSON.parse as soon as the asset has// finished loading}},// Once the assets are done loading, then we can use them within our// applicationonDone:(assets)=>{console.log(assets.scores)document.body.appendChild(assets.some_video)document.body.appendChild(assets.an_image)console.log(assets.json_data)},// As assets are preloaded the progress callback gets firedonProgress:(progress,message)=>{document.body.innerHTML='<b>'+(progress*100)+'% loaded</b>: '+message},onError:(err)=>{console.error(err)}})
The easiest way to installresl is to use npm:
npm install reslresl takes a single configuration object as input. At minimum this object must specify a callback which is executed once asset loading is finished and a manifest of assets which must be loaded. Theconfig object accepts the following properties:
| Config parameter | Interpretation |
|---|---|
manifest | (Required) An object listing each resource to be loaded.For more details see below |
onDone(assets) | (Required) A callback which is executed once all assets have loaded. This is passed a dictionary of all assets. |
onProgress(progress, message) | A callback which is executed each time more assets are loaded. Gets passed two arguments: progress so far as a fraction of the total bundle and a message related to the most recent progress event. |
onError(error) | A callback which is executed if any errors are encountered during preloading. Gets passed the last error which occurred. |
Each entry in the manifest is an object specifying the location (URL) of an asset, its type and some optional data related to parsing the asset. User definedparsers can be added to assets to help streamline loading resources.
| Manifest parameter | Interpretation | Default |
|---|---|---|
src | (Required) The URL of the asset | N/A |
type | Thetype of the asset. | 'text' |
parser | An optionalparser (see below) | null |
stream | If set to true, then the resource is streamed. | false |
credentials | If set to true, then pass credentials to cross origin requests | false |
The following resource types are currently supported byresl:
| Resource type | Interpretation |
|---|---|
'text' | A UTF string loaded via XHR |
'binary' | Binary array buffer loaded via XHR |
'image' | AnHTML image element |
'video' | AnHTML video element |
'audio' | An HTML audio element |
A manifest entry may take an optional parser object as input which transforms the base asset into some other data type. There are two ways to specify a parser inresl:
- As a function
parser(data)which takes as input the data and returns the encoded object. - As an object which implements the following interface:
| Callback | Effect |
|---|---|
onData(data) | (Required) A callback which is fired each time new data is available in the stream |
onDone() | A callback which is fired once the stream is finished loading |
(c) 2016 Mikola Lysenko. MIT License