JavaScript 函数在两个不同的时间间隔给出两种不同的结果

Question

I tried to look about this problem but didn't quite understand why does my code log out the first assignment before the delay and logs out the second assignment after the delay

let myName = 'John';
delayer();
myName = 'Robert';
function delayer() {
    console.log(myName);
    setTimeout(() => console.log(myName), 1500)
}

Answer 1

() => console.log(myName) is the same as function() { return console.log(myName); } function() { return console.log(myName); } . ^[1]

The resulting function reference is passed to setTimeout which arranges to call it after the specified delay. setTimeout doesn't wait for the delay to occur before returning. It returns immediately. So myName has been changed by the time the anonymous function has been called.

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1. There are differences between the two approaches as itemized in the first link, but they don't come into play here.