Package Exports

exec.js

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Readme

Cancellable Javascript Code Runner

A high performance and low latency javascript code runner that enables to isolate and abort javascript code execution, including setTimeout/setInterval, promises and Fetch requests. It supports most browsers including IE.

WebWorkers have a startup latency of ~40ms which make them unsuitable for some applications. This code runner does not have a significant latency or overhead and it's 690 bytes compressed.

In some modern browsers the code may be executed in a separate thread (multithreading) without the latency disadvantage of WebWorkers and with less code. (see Chrome OOPIF)

The code is executed in an isolated container which may provide security advantages.

Install

with npm:

npm install exec.js

with bower:

bower install exec.js

Usage

Include exec.js in the HTML document.

<script src="exec.min.js" />

Use var runner = new exec(your code); to execute javascript code in an isolated container. It returns a promise. You can return data from your code using the returnData() function. You can return transferable objects such as ArrayBuffer to enable low latency and high performance processing of large objects. (more info)

Simple Fetch request

var runner = new exec(function() {
    fetch('https://ajax.googleapis.com/ajax/libs/angularjs/1.6.4/angular.min.js')
        .then(function(response) {
            response.text().then(function(text) {
                returnData(text);
            });
        }).catch(function(err) {
            console.log(err.message);
        });
}).then(function(data) {
    console.log('fetch result', data);
});

// timeout in 5 seconds
setTimeout(function() {
    runner.stop(); // cancel Fetch request
},5000);

Advanced Fetch request

var runner = new exec(function() {
    fetch('https://ajax.googleapis.com/ajax/libs/angularjs/1.6.4/angular.min.js')
        .then(function(response) {

            // return original Fetch response

            // headers
            var headers = {};
            for (key of response.headers.keys()) {
                headers[key] = response.headers.get(key);
            }

            // return transferable arraybuffer
            // @link https://developers.google.com/web/updates/2011/12/Transferable-Objects-Lightning-Fast
            response.arrayBuffer()
                .then(function(buffer) {
                    returnData({
                        buffer: buffer,
                        headers: headers,
                        status: response.status,
                        statusText: response.statusText
                    }, buffer);
                });
        }).catch(function(err) {
            console.log(err.message);
        });
}).then(function(data) {

    // reconstruct Fetch response from arraybuffer
    var response = new Response(
        data.buffer, {
            headers: new Headers(data.headers),
            status: data.status,
            statusText: data.statusText
        }
    );
    console.info('fetch response', response);

    // response text
    response.text()
        .then(function(text) {
            console.info('fetch data', text.length);
        });

});

// timeout in 5 seconds
setTimeout(function() {
    runner.stop(); // cancel Fetch request
},5000);

Abort / cancel code execution

To cancel code execution, use runner.stop().

var runner = new exec('setInterval(function() {console.log(123);},100);');
setTimeout(function() {
    runner.stop();
},1000);

Internet Explorer

For IE a Promise polyfill is required. The code could be modified to use a callback instead of a promise.