Three practical new features from JavaScript engine V8 8.5

This article was reproduced from the public number: Code Secret Garden

JavaScript Engine V8 is released in version 8.5, and let's take a look at the three practical features of version 8.5.

Promise.any

Promise adds an any method that receives a Promise array, and when one of the Promise in the array is fulfilled the Promise it returns is returned.

const promises = [
  fetch('/endpoint-a').then(() => 'a'),
  fetch('/endpoint-b').then(() => 'b'),
  fetch('/endpoint-c').then(() => 'c'),
];
try {
  const first = await Promise.any(promises);
  // 任何一个 Promise 为 fulfilled 状态
  console.log(first);
  // →   'b'
} catch (error) {
  // 所有 Promise 都被 rejected 了
  console.assert(error instanceof AggregateError);
  // reject 结果数组
  console.log(error.errors);
}

If all Promise of Promise are rejected, Promise.any returns an exception of AggregateError type, which errors all Promise rejected properties.

Be careful not to confuse with Promise.race race which returns if any one of Promise in the array is resolved or rejected, while any method must have a resolution that throws an exception if all are rejected.

String.prototype.replaceAll

String.prototype.replaceAll provides an easy way to replace all matches for substrings without creating a global RegExp

Looking at the following example, before you're going to replace all of the + in queryString you need to create a global rule:

const queryString = 'q=query+string+parameters';


queryString.replace(/\+/g, ' ');

Now you just need to use replaceAll method:

queryString.replaceAll('+', ' ');

The logical assignment operator

The logical assignment operator is a new compound assignment operator that allows him to manipulate logic &&，||或?? Combine with an assignment into a command.

x &&= y;
// 等同于 x && (x = y)
x ||= y;
// 等同于 x || (x = y)
x ??= y;
// 等同于 x ?? (x = y)

Here's a look at W3Cschool编程狮 introduction to the three practical new features that JavaScript engine V8 8.5 brings.