如何在javascript中对此查询使用AJAX调用？ （选择*从问题所在的地方，问题数=问题数）；

Question

这是我需要通过AJAX调用获得的搜索查询，

(SELECT * FROM questions WHERE questions_number = questions _number);

这是我将在其中使用的脚本

var m = new Map();


function randomize_questions(){

    while(m.size <= 20)
    {
        const x = parseInt(Math.random()*100);
        m.has(x) ? randomize_questions() : m.set(x,x); 
    }
    m.foreach( el => {
        const question_number = m.get(el);
     //Query->
    });

}

randomize_questions();

希望你们可以提供帮助：）

Answer 1

1. 对于您的JS函数randomize_questions，为什么要使用递归？您最终可能会获得20层深的堆栈，并且在填充了地图之后，它将在20种元素中运行20次，以进行AJAX调用-在最坏的情况下，即对服务器进行400次AJAX调用场景。一个更简单的方法是：

   const random_number = () => {
     return parseInt(Math.random()*100);
   }
   const randomize_questions = async () => {
     var x;
     while(m.size <= 20) {
       x = random_number();
       while(m.has(x)) {
         x = random_number();
       }
       m.set(x,x);
     }
   };
   
   const get_questions = async () => {
     m.foreach(index => {
       // Perform AJAX call
       // You can fill this in :)
     });
   };
   
   await randomize_questions();
   await get_questions();
   

2. 在服务器端，您会遇到类似这样的事情：

   <?php
   // Instantiate your DB connection, do validation that 
   // the request came from your page etc. Unfortunately
   // outside the scope of your question :)
   $question_id = $_GET['question_id'];
   
   // Going to assume you are using PDO with MySQL
   $stmt = $pdo->prepare('SELECT * FROM questions WHERE questions_number = ?');
   $stmt->execute([$question_id]);
   $question = $stmt->fetch(PDO::FETCH_ASSOC);
   // Return the data as needed, most probably as a JSON object
   echo json_encode($question);
   ?>