如何在递归方法中进行同步调用？

Question

我正在尝试运行调用并阻止递归函数在完成另一个函数之前继续运行。

我试过使用 promise，但我只是不明白要在 .then() 部分中放入什么作为递归调用。

    const htmlString = '<table><tr><td>Bah</td><td>Pooh</td></tr></table>';
    const fragment = 
    document.createRange().createContextualFragment(htmlString);

    function walkTheDOM(node, func) {
        func(node);
        node = node.firstChild;
        while (node) {
            walkTheDOM(node, func);
            node = node.nextSibling;
        }
    }

    function asynchronousCallWantingtoMakeSynchronous() {
       return new Promise((resolve, reject) => {
           setTimeout(function() {
       return resolve ( console.log("should come before another recursive call"))
           }, 0)
       });
    }

    walkTheDOM(fragment, function(node) {
        console.log(node)
        asynchronousCallWantingtoMakeSynchronous.then(function(){

        })
    })

实际打印出的内容：

    <table>...</table>
    <tr>...</tr>
    <td>Bah</td>
    "Bah"
    <td>Pooh</td>
    "Pooh"
    "should come before Pooh"

我真正想要的是：

    <table>...</table>
    "should come before another recursive call"
    <tr>...</tr>
    "should come before another recursive call"
    <td>Bah</td>
    "should come before another recursive call"
    "Bah"
    "should come before another recursive call"
    <td>Pooh</td>
    "should come before another recursive call"
    "Pooh"
    "should come before another recursive call"

记住，setTimeout 只是一个例子，我只是想让异步调用同步。

Answer 1

无法使异步函数同步。但是您可以使用 Promises 或 async-await 让它感觉更像一点。你可以用这些来穿插你的电话

const htmlString = '<table><tr><td>Bah</td><td>Pooh</td></tr></table>';
const fragment = document.createRange().createContextualFragment(htmlString);

async function asyncWalkTheDOM(node, func, intersperse) {
    func(node);
    node = node.firstChild;
    while (node) {
        await intersperse(node)
        asyncWalkTheDOM(node, func, intersperse);
        node = node.nextSibling;
    }
}

async function asynchronousCall(node) {
  return new Promise(function (res, rej) { 
    setTimeout(function() {
      console.log("should come before another recursive call")
      res(node)
    }, 0)
  })
}

asyncWalkTheDOM(fragment, function(node) {
    console.log(node.nodeName)
}, asynchronousCall)

如何在递归方法中进行同步调用？

How do I make a synchronous call in a recursive method?

javascript

recursion

synchronous

promise

async-await