1 分钟倒计时 JavaScript

Question

我正在尝试构建一个打字测试，当用户按下文本区域中的按键时，该测试就开始倒计时。我认为 if-else 循环有助于在 HTML 中显示并启动 1 分钟倒计时器，但事实并非如此。

请向我解释我做错了什么以及如何纠正我的代码。

HTML：

<div id="timer"></div>
<p>Text for typing test will go here.</p>
<textarea id="textarea" rows="14" cols="150" placeholder="Start typing here...">
</textarea>`

JS：

var seconds=1000 * 60; //1000 = 1 second in JS
var min = seconds * 60;
var textarea = document.getElementById("textarea").onkeypress = function() { 
    myFunction()
};
//When a key is pressed in the text area, update the timer using myFunction

function myFunction() {
   document.getElementById("timer").innerHTML = 
     if (seconds>=0) {
         seconds = seconds--;
     } else {
         clearInterval("timer");
         alert("You type X WPM");
     }
} //If seconds are equal or greater than 0, countdown until 1 minute has passed
//Else, clear the timer and alert user of how many words they type per minute

document.getElementById("timer").innerHTML="0:" + seconds; 

Answer 1

您的代码中有很多语法错误。您需要使用setIntervalfunction 来启动函数的连续调用。更重要的是，

var seconds = 1000 * 60; //1000 = 1 second in JS
var min = seconds * 60;

这些计算是另一个问题。

1000 * 60意思是60 seconds，所以seconds * 60给你60 minutes。

正如其中一位评论所说，there are syntax errors all over the place.. 您需要更深入地了解使用 JavaScript 进行编码。

var seconds = 1000 * 60; //1000 = 1 second in JS
var min = seconds * 60;

var seconds = 1000 * 60; //1000 = 1 second in JS
var textarea = document.getElementById("textarea");
var timer;
textarea.addEventListener("keypress", myFunction)
//When a key is pressed in the text area, update the timer using myFunction

function myFunction() {
   textarea.removeEventListener("keypress", myFunction);
   if(seconds == 60000)
     timer = setInterval(myFunction, 1000)
   seconds -= 1000;
   document.getElementById("timer").innerHTML = '0:' + seconds/1000;
   if (seconds <= 0) {
       clearInterval(timer);
       alert("You type X WPM");
   }
} //If seconds are equal or greater than 0, countdown until 1 minute has passed
//Else, clear the timer and alert user of how many words they type per minute

document.getElementById("timer").innerHTML= "0:" + seconds/1000;

Answer 2

我注意到您的解决方案存在一些问题。

1）你clearInterval，但你从未setInterval

2)秒=秒--，由于JavaScript中的操作顺序，它并没有像你想象的那样做。

我修改了你的 JS，并在这个codepen中有一个可行的解决方案

JS：

var seconds=60;
var timer;
function myFunction() {
  if(seconds < 60) { // I want it to say 1:00, not 60
    document.getElementById("timer").innerHTML = seconds;
  }
  if (seconds >0 ) { // so it doesn't go to -1
     seconds--;
  } else {
     clearInterval(timer);
     alert("You type X WPM");
  }
}
document.getElementById("textarea").onkeypress = function() {
  if(!timer) {
    timer = window.setInterval(function() { 
      myFunction();
    }, 1000); // every second
  }
} 

document.getElementById("timer").innerHTML="1:00";