Runs a function in a separate thread by using a Web Worker, allowing long running functions to not block the UI.
Create a new Worker
using a Blob
object URL, the contents of which should be the stringified version of the supplied function.
Immediately post the return value of calling the function back.
Return a promise, listening for onmessage
and onerror
events and resolving the data posted back from the worker, or throwing an error.
代码片段
const runAsync = fn => {
const worker = new Worker(
URL.createObjectURL(new Blob([`postMessage((${fn})());`]), {
type: 'application/javascript; charset=utf-8'
})
);
return new Promise((res, rej) => {
worker.onmessage = ({ data }) => {
res(data), worker.terminate();
};
worker.onerror = err => {
rej(err), worker.terminate();
};
});
};
使用样例
const longRunningFunction = () => {
let result = 0;
for (let i = 0; i < 1000; i++)
for (let j = 0; j < 700; j++) for (let k = 0; k < 300; k++) result = result + i + j + k;
return result;
};
/*
NOTE: Since the function is running in a different context, closures are not supported.
The function supplied to `runAsync` gets stringified, so everything becomes literal.
All variables and functions must be defined inside.
*/
runAsync(longRunningFunction).then(console.log); // 209685000000
runAsync(() => 10 ** 3).then(console.log); // 1000
let outsideVariable = 50;
runAsync(() => typeof outsideVariable).then(console.log); // 'undefined'