Detailed explanation of the usage of ES6

The () method is also to wrap multiple Promise instances into a new Promise instance.

const p = ([p1, p2, p3]);

In the above code, as long as an instance in p1, p2, and p3 is the first to change the state, the state of p will change as a result. The return value of the Promise instance that was first changed is passed to the callback function of p.

The parameters of the () method are the same as the () method. If it is not a Promise instance, the () method mentioned below will be called first, convert the parameters into a Promise instance, and then further processing.

    let x = 10;
    let p1 = new Promise((resolve) =&gt; {
       setTimeout(()=&gt;resolve("p1 hello" + x),2000);
    })
        .then((res) =&gt; {
            (`p1 then Output${res}`);
            return res;
        });
    let p2 = new Promise((resolve) =&gt; {
        setTimeout(()=&gt; resolve("p2 hello" + x),2000);;
    })
        .then((res) =&gt; {
            (`p2 then Output${res}`);
            return res;
        });
    let p3 = new Promise((resolve) =&gt; {
        setTimeout(()=&gt;resolve("p3 hello" + x),2000);;
    })
        .then((res) =&gt; {
            (`p3 then Output${res}`);
            return res;
        });
    let p4 = new Promise((resolve) =&gt; {
        setTimeout(()=&gt;resolve("p4 hello" + x),2000);;
    })
        .then((res) =&gt; {
            (`p4 then Output${res}`);
            return res;
        });
    ([p1, p2, p3, p4])
        .then(result =&gt; (result))
        .catch((e) =&gt; {
            ("f*cking man reported an error");
            (e);
        });

Output result: Only the Promise that changed the state first

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