Node.js：如何防止下一行执行，直到我的 forLoop 给我结果

Question

let a = []
    for (let i=0;i<4;i++){
        setTimeout(()=>{
            a.push(i);
        },2000)
    }


console.log(a);

Here I am getting a always blank []. Please suggest a way to stop executing console.log(a) line until a gets filled.

Answer 1

You should await setTimeout :

let a = [];
async function test() {
  for (let i = 0; i < 4; i++) {
    await new Promise((resolve) =>
      setTimeout(() => {
        a.push(i);
        resolve();
      }, 2000)
    );
  }
}

await test();

console.log(a);

Note: You can also use Promise.allSettled to run them at the same time