Internals of async / await in JavaScript(akashhamirwasia.com)

    setTimeout(() => console.log('hello'), 0)
    console.log('world')

    async function executeQueue(promises, concurrentLimit) {
      let index = 0;
      let activePromises = [];

      async function manageQueue() {
        if (index >= promises.length && activePromises.length === 0) return;

        while (activePromises.length < concurrentLimit && index < promises.length) {
          const promise = promises[index]();
          activePromises.push(promise);
          index++;

          promise.then(() => {
            activePromises = activePromises.filter(p => p !== promise);
            manageQueue();
          });
        }
      }

      await manageQueue();
      await Promise.all(activePromises);
    }

    function r(i, resolve) {
      console.log(`Task ${i}`)
      resolve(`Task ${resolve}`)
    }

    // Example usage
    const promises = [
      () => new Promise(resolve => setTimeout(() => r("Task 1", resolve), 2000)),
      () => new Promise(resolve => setTimeout(() => r("Task 2", resolve), 1000)),
      () => new Promise(resolve => setTimeout(() => r("Task 3", resolve), 3000)),
      () => new Promise(resolve => setTimeout(() => r("Task 4", resolve), 500)),
      () => new Promise(resolve => setTimeout(() => r("Task 5", resolve), 1500))
    ];

    executeQueue(promises, 4).then(() => {
      console.log("All tasks completed!");
    });

    "Task Task 4"
    "Task Task 2"
    "Task Task 1"
    "Task Task 5"
    "Task Task 3"
    "All tasks completed!"