[英]HTML and Javascript, window.prompt
對javascript和html類型的東西非常新。 我只想舉一個使用用戶輸入並將其輸出到表中的簡單示例。 我在獲取窗口提示時遇到了麻煩。 我想我確實在做錯事,但我目前還沒有看到……我正在學校上課,但這不是家庭作業,只是我自己做的練習。
這與while循環有關嗎? 關於我應如何繼續提示用戶直到他們另有說明的任何建議?
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Mileage Record</title>
<style type = "text/css">
table {
width:300px;
border-collapse:collapse;
background-color:lightblue;
}
table, td, th {
border: 1px solid black;
padding: 4px;
}
th {
text-align: left;
color: white;
background-color: darkblue
}
tr.oddrow {
background-color: white;
}
</style>
<script>
var milesDriven;
var gallonsUsed;
var mpg;
var anyMore;
document.writeln("<table>");
document.writeln("<thead><tr><th>Miles Driven</th>");
document.writeln("<th>Gallons Used</th>");
document.writeln("<th>MPG</th>");
document.writeln("</tr></thead><tbody>");
while (anyMore == true) {
milesDriven = window.prompt("How many miles did you drive?");
gallonsUsed = window.prompt("How many gallons did you use?");
mpg = milesDrive/gallonsUsed;
document.writln("<tr><td>" + milesDriven + "</td><td>" +
gallonsUsed + "</td><td>" + mpg + "</td></tr>");
anymore = confirm("Do you have any more data to input?");
}
document.writeln("</tbody></table>");
</script>
該方法存在幾個問題。 您不應使用document.writeln()
來修改文檔內容。 而是創建元素並將其添加到文檔樹中。 一個好的JavaScript教程應該告訴您如何做到這一點。 它還將解釋標識符是區分大小寫的,所以你不能只寫anyMore
這里anymore
那里。 您在標識符中也有其他錯別字。 而且,由於未定義的值不等於true
,因此永遠不會執行循環。
<pre>
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Mileage Record</title>
<style type = "text/css">
table {
width:300px;
border-collapse:collapse;
background-color:lightblue;
}
table, td, th {
border: 1px solid black;
padding: 4px;
}
th {
text-align: left;
color: white;
background-color: darkblue
}
tr.oddrow {
background-color: white;
}
</style>
<script>
// var milesDriven;
// var gallonsUsed;
// var mpg;
var anyMore=0;
var str="<table>";
str+="<thead><tr><th>Miles Driven</th>";
str+="<th>Gallons Used</th>";
str+="<th>MPG</th>";
str+="</tr></thead><tbody>";
function milesDriven(){
return window.prompt("How many miles did you drive?");
}
function gallonsUsed(){
return window.prompt("How many gallons did you use?");
}
function mpg(){
return milesDriven()/gallonsUsed();
}
function addComponentsToDOM(){
while (anyMore<3) { //not 0 is true or not undefined is true or not null is true
str+="<tr><td>" + milesDriven() + "</td><td>" +
gallonsUsed() + "</td><td>" + mpg() + "</td></tr>"
// anymore = confirm("Do you have any more data to input?");
anyMore++;
}
str+="</tbody></table>";
//document.writeln(); i suggest you not use this method add component to DOM tree
//because this method first empty DOM tree content
document.body.innerHTML=str;
}
//why use this event,because window after loaded document.body not null
window.onload=addComponentsToDOM;
</script>
</pre>
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