如何將我的代碼修改為異步的？

Question

下面，我寫了一個 function ，它接受一個數組和一個鍵來搜索並計算鍵與數組中元素匹配的次數。 我正在嘗試修改我的 function 以異步計算匹配數，但不知道如何最好地處理 go。 任何見解或示例將不勝感激。

我的代碼：

function countMatches(arr, key) 
{ 
    var count=0; 
    var i; 
    for (i=0; i < arr.length; i++) 
    { 
        if(arr[i] == key) count=count+1; 
    } 
    return count; 
}

let arr1 = [3, 2, 4, 6, 1, 1, 6, 8, 9];
console.log(countMatches(arr1, 6));

Answer 1

使用Promise

 function countMatches(arr, key) { return new Promise((resolve) => { var count=0; var i; for (i=0; i < arr.length; i++) { if(arr[i] == key) count=count+1; } resolve(count); }); } let arr1 = [3, 2, 4, 6, 1, 1, 6, 8, 9]; countMatches(arr1, 6).then(result => console.log(result));

Answer 2

您可以通過使用async關鍵字將其轉換為異步function 從任何同步 function 返回 promise：

 /** This is a sync function */ function getNumber1 () { return 42; } const n1 = getNumber1(); console.log({sync: n1}); // 42 /** This is an async function Notice the `async` keyword before `function` It automatically returns a promise which resolves to the value vvvvv */ async function getNumber2 () { return 42; } getNumber2().then(n2 => console.log({async: n2})); // 42

Answer 3

異步/等待

async function  countMatchesAsync(arr, key) 
{ 
    var count=0; 
    var i; 
    for (i=0; i < arr.length; i++) 
    { 
        if(arr[i] == key) count=count+1; 
    } 
    return await count; 
}

let arr1 = [3, 2, 4, 6, 1, 1, 6, 8, 9];
countMatchesAsync(arr1, 6).then(console.log);