Question

＆＃13;

var cars = ["BMW", "Volvo", "Saab", "Ford"];
var text = "33";
var i;
for (i = 0; i < cars.length; i++) {
text += cars[i] + "<br>";
}

document.getElementById("demo").innerHTML = text;

＆＃13;

<p id="demo"></p>

＆＃13;

嗨，我希望更好地理解JavaScript，并且我对for循环中的这个变量感到困惑。为什么结果不会在集合中的每个结果中添加文本的值？

33bmw
Volvo
Saab
Ford

为什么不是这个..

33bmw
33Volvo
33Saab
33Ford

Answer 1

这是因为您将每个cars项添加到text。在第一次迭代后，text不再只是33。它的33BMW。

您需要的是：

var cars = ["BMW", "Volvo", "Saab", "Ford"];
var text = "33";
var result = "";  // add a special variable to store both `text` and `car` name
var i;
for (i = 0; i < cars.length; i++) {
    result += text + cars[i] + "<br>";  // use it here
}

document.getElementById("demo").innerHTML = result;   // and here

Answer 2

您正在将文本初始化为“33”。然后对于每辆车，您将汽车的名称（car [i]）和br添加到文本中。你想要的是将文本初始化为“”。然后为每辆车添加“33”。

var cars = ["BMW", "Volvo", "Saab", "Ford"];
var text = "";
var i;
for (i = 0; i < cars.length; i++) {
    text += "33" + cars[i] + "<br>";
}

document.getElementById("demo").innerHTML = text;

Answer 3

在代码中的评论中回答

＆＃13;

//array of strings
var cars = ["BMW", "Volvo", "Saab", "Ford"];
// sets the variable text to "33"
var text = "33";
var i;
// loops through the strings in cars variable
for (i = 0; i < cars.length; i++) {
    // adds car string + <br> to text
    // first pass is 33BMW<br>
    // second pass is 33BMW<br>Volvo<br> 
    // third pass is 33BMW<br>Volvo<br>Saab<br>
    // fourth pass is 33BMW<br>Volvo<br>Saab<br>Ford<br>
    text += cars[i] + "<br>";
}

// writes the text to an html element
document.getElementById("demo").innerHTML = text;

＆＃13;

<p id="demo"></p>

＆＃13;

<强>解决方案创建一个33的前缀，然后将其附加到循环中，使其位于每一行

＆＃13;

//array of strings
var cars = ["BMW", "Volvo", "Saab", "Ford"];
var text = "";
var prefix = "33";
var i;
// loops through the strings in cars variable
for (i = 0; i < cars.length; i++) {
    text += prefix + cars[i] + "<br>";
}

// writes the text to an html element
document.getElementById("demo").innerHTML = text;

＆＃13;

<p id="demo"></p>

＆＃13;

Answer 4

这会给你想要的结果：

var cars = ["BMW", "Volvo", "Saab", "Ford"];
var prefix = "33";
var text = "";
var i;
for (i = 0; i < cars.length; i++) {
text += prefix  + cars[i] + "<br>";
}

Answer 5

var cars = ["BMW", "Volvo", "Saab", "Ford"];
var text = "33";
var output;
var i;
for (i = 0; i < cars.length; i++) {
output += (text + cars[i]) + "<br>";
}

应该是你的代码。 text = text + cars [0]创建33BMW。下一次迭代将沃尔沃加到33BMW而不是33VMW到33BMW。

Answer 6

你必须在汽车的每个值中连接文本。

Answer jsfiddle

新脚本

var cars = ["BMW", "Volvo", "Saab", "Ford"];
var text = "33";
var out_text = '';

out_text = cars.map(function(i){
    return text + i;
}).join( "<br/>");
document.getElementById("demo").innerHTML = out_text;

您的脚本：

var cars = ["BMW", "Volvo", "Saab", "Ford"];
var text = "33";
var i; 
var out_text = '';
for (i = 0; i < cars.length; i++) {
    out_text = text + cars[i] + "<br>";
}

<强>输出：

33BMW
  33Volvo
  33Saab
  33Ford

document.getElementById("demo").innerHTML = out_text;

for循环中的变量

6 个答案: