Javascript中异步递归函数块内部是否有同步函数调用?

简短的回答是“ 对 “我的意思是, foo() 哪个同步将被阻止 bar() 执行至 foo() 完成。但是,作为 bar() 是异步的,那么 foo() 不会阻止外部代码 bar() .

const delay = 3000; // 3 seconds of delay.

function foo() {
    console.log('Is bar waiting for me to finish?');
    console.log('Answer: Yes!');
}

async function bar() {
    await new Promise((r) => setTimeout(r, delay)); // waits `delay` and `foo()`.
    foo(); // is this blocking? r: yes
    await new Promise((r) => setTimeout(r, delay)); // waits `delay` and loop.
    await bar(); // loops.
}

// Will not block the lines that follows:
bar();

// Unblocked line.
console.log('I am not blocked by `bar()`.');

对, foo() 将在等待电话之前完成 bar() . foo() JavaScript执行在同步函数中逐行进行。wait关键字只会暂停async函数内的执行 bar() 之后 foo() 已经完成了。

您可以通过添加(模拟)一些延迟来验证这一点。

function foo() {
    console.log('is bar waiting for me to finish?');
    let start = Date.now();
    while (Date.now() - start < 5000) {} // Simulate delay
    console.log('foo finished');
}

async function bar() {
    console.log('calling foo');
    foo();
    console.log('foo returned');
    await new Promise((r) => setTimeout(r, 10));
    console.log('timeout finished');
    // Preventing infinite recursion, just for testing
    //await bar();
}

bar();