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做出决策：认识 if-else

通过构建一个智能恒温器来学习 JavaScript 的 if-else 语句，该恒温器会决定是否开启加热或空调。

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做出决策：认识 if-else

通过构建一个智能恒温器来学习 JavaScript 的 if-else 语句，该恒温器会决定是否开启加热或空调。

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JavaScript 中的 if-else 语句

1let age = Number(prompt("How old are you?"));
2
3if (age >= 18) {
4  console.log("You can vote!");
5} else {
6  console.log("Sorry, too young.");
7}
1let temperature = 15;
2
3if (temperature < 18) {
4  console.log("Switch to Fan mode");
5} else {
6  console.log("Keep cooling");
7}
1let currentTemperature = 15;
2let preferredTemperature = 18;
3
4if (currentTemperature < preferredTemperature) {
5  console.log("Switch to Fan mode");
6} else {
7  console.log("Keep cooling");
8}
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Hey AI, 将我的基于控制台的恒温器程序转换为网页。添加两个输入框，分别用于当前温度和期望温度。当我点击按钮时，它应比较这两个值，并显示“Switch to Fan mode”或“Keep cooling”。 以下是代码：

1let currentTemperature = 15;
2let preferredTemperature = 18;
3
4if (currentTemperature < preferredTemperature) {
5  console.log("Switch to Fan mode");
6} else {
7  console.log("Keep cooling");
8}

Hey AI, 将我的基于控制台的恒温器程序转换为网页。添加两个输入框，分别用于当前温度和期望温度。当我点击按钮时，它应比较这两个值，并显示“Switch to Fan mode”或“Keep cooling”。 以下是代码：

1let currentTemperature = 15;
2let preferredTemperature = 18;
3if (currentTemperature < preferredTemperature) {
4console.log("Switch to Fan mode");
5} else {
6console.log("Keep cooling");
7}

No configuration found for ID: af882f7e2f56463eee3df4670d19c4db31286c5a2cca36c42da640f115c76528

1<!DOCTYPE html>
2<html>
3<head>
4  <title>Smart Thermostat Advisor</title>
5</head>
6<body>
7  <h2>Smart Thermostat Advisor</h2>
8
9  <!-- Input field for current temperature -->
10  Current Temperature: <input type="number" id="current"><br>
11
12  <!-- Input field for preferred temperature -->
13  Preferred Temperature: <input type="number" id="preferred"><br>
14
15  <!-- Button that checks advice -->
16  <button onclick="
17    let current = Number(document.getElementById('current').value);
18    let preferred = Number(document.getElementById('preferred').value);
19
20    let advice;
21    if (current < preferred) {
22      advice = 'Switch to Fan mode';
23    } else {
24      advice = 'Keep cooling';
25    }
26
27    document.getElementById('result').innerHTML = advice;
28  ">
29    Check Advice
30  </button>
31
32  <!-- Paragraph where the advice will be shown -->
33  <p id="result"></p>
34</body>
35</html>
1<!DOCTYPE html>
2<html>
3<head>
4  <title>Smart Thermostat Advisor</title>
5</head>
6<body>
7  <h2>Smart Thermostat Advisor</h2>
8
9  <!-- Input field for current temperature -->
10  Current Temperature: <input type="number" id="current"><br>
11
12  <!-- Input field for preferred temperature -->
13  Preferred Temperature: <input type="number" id="preferred"><br>
14
15  <!-- Button that checks advice -->
16  <button onclick="
17    let current = Number(document.getElementById('current').value);
18    let preferred = Number(document.getElementById('preferred').value);
19
20    let advice;
21    if (current < preferred) {
22      advice = 'Switch to Fan mode';
23    } else {
24      advice = 'Keep cooling';
25    }
26
27    document.getElementById('result').innerHTML = advice;
28  ">
29    Check Advice
30  </button>
31
32  <!-- Paragraph where the advice will be shown -->
33  <p id="result"></p>
34</body>
35</html>

代码示例

1Current: 25  
2Preferred: 18  
3Advice: Keep cooling  
4Tip: Consider adjusting gradually to save energy.

No configuration found for ID: d8be91dd74ff1e97a5a4ed05c935144c1d71f5b796dd62dc0f972e9407437c37

1<!DOCTYPE html>
2<html>
3<head>
4  <title>Thermostat with Energy Saver Tip</title>
5</head>
6<body>
7  <h2>Thermostat with Energy Saver</h2>
8
9  Current Temperature: <input type="number" id="current"><br>
10  Preferred Temperature: <input type="number" id="preferred"><br>
11
12  <button onclick="
13    let current = Number(document.getElementById('current').value);
14    let preferred = Number(document.getElementById('preferred').value);
15
16    let advice;
17    if (current < preferred) {
18      advice = 'Switch to Fan mode';
19    } else {
20      advice = 'Keep cooling';
21    }
22
23    let message = 'Advice: ' + advice;
24
25    if (Math.abs(current - preferred) > 5) {
26      message += '<br>Tip: Consider adjusting gradually to save energy.';
27    }
28
29    document.getElementById('result').innerHTML = message;
30  ">
31    Check Advice
32  </button>
33
34  <p id="result"></p>
35</body>
36</html>
1<!DOCTYPE html>
2<html>
3<head>
4  <title>Thermostat with Energy Saver Tip</title>
5</head>
6<body>
7  <h2>Thermostat with Energy Saver</h2>
8
9  Current Temperature: <input type="number" id="current"><br>
10  Preferred Temperature: <input type="number" id="preferred"><br>
11
12  <button onclick="
13    let current = Number(document.getElementById('current').value);
14    let preferred = Number(document.getElementById('preferred').value);
15
16    let advice;
17    if (current < preferred) {
18      advice = 'Switch to Fan mode';
19    } else {
20      advice = 'Keep cooling';
21    }
22
23    let message = 'Advice: ' + advice;
24
25    if (Math.abs(current - preferred) > 5) {
26      message += '<br>Tip: Consider adjusting gradually to save energy.';
27    }
28
29    document.getElementById('result').innerHTML = message;
30  ">
31    Check Advice
32  </button>
33
34  <p id="result"></p>
35</body>
36</html>

变量、数据类型和输入

Else-If 链和嵌套