Question

此功能：

function print(){
  console.log('num 1')

  setTimeout(() => {
    global.name = 'max'
    console.log('num 2')
  },9000);

  console.log('num 3');
}
print();
console.log(global.name)

为此而骄傲：

num 1
num 3
undefined
num 2

我需要：

打印num 1
等到9秒钟
设置global.name = max
打印num 2
打印num 3
console.log(global.name)
打印max而不打印undefined

我用python编写了这段代码，并逐行执行因为没有所谓的同步和异步。

我需要像python（一行一行）那样执行这段代码

Answer 1

JavaScript代码逐行执行。如果您想执行一段代码，则仍然需要将给定的行放入超时中，如下所示：

let name = "Unknown";

function print() {
    console.log('num 1');

    setTimeout(() => {
        this.name = 'max';
        console.log('num 2');
        console.log('num 3');
        console.log(this.name);

    }, 900);


}

print();

Answer 2

在JavaScript中使用同步性最易读的方式是使用异步函数。让您了解它的外观：

// To simulate the function you're going to use the snippet in
(async () => {

  async function print(){
    console.log('num 1')

    // await stops the execution until the setTimeout in sleep is done (non blocking)
    await sleep(9000);

    global.name = 'max'
    console.log('num 2')

    console.log('num 3');
  }

  // wait for the print function to finish
  await print();

  console.log(global.name)

})();

// Little utility function
function sleep(time) {
  return new Promise(resolve => setTimeout(resolve, time))
}

您可以在此处了解有关异步/等待的更多信息：https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/async_function

Node js在完成多行代码之前执行功能

2 个答案: