JavaScript Uncaught TypeError Cannot read property 'value'
用JavaScript操作DOM时出现如下错误：
Uncaught TypeError: Cannot set property 'value' of null Uncaught TypeError: Cannot read property 'id' of undefined- 1
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例如：
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8" /><script> var div = document.getElementById("测试1"); alert(div.id); alert(div.className); alert(div.title);</script><title>测试</title></head><body> <div id="测试1" class="测试2" title="测试3"> <span>0</span> <span>1</span> <span>2</span> <span>3</span> </div></body></html>- 1
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运行时出现如下错误：
问题出在JS运行的时候你的页面还没有加载完成，所以你的JS代码找不到你的页面元素，就会抛出这个问题。解决办法就是把JavaScript代码放在body的最后，例如：
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8" /><title>测试</title></head><body> <div id="测试1" class="测试2" title="测试3"> <span>0</span> <span>1</span> <span>2</span> <span>3</span> </div><script> var div = document.getElementById("测试1"); alert(div.id); alert(div.className); alert(div.title);</script></body></html>- 1
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用JavaScript操作DOM时出现如下错误：
Uncaught TypeError: Cannot set property 'value' of null Uncaught TypeError: Cannot read property 'id' of undefined- 1
- 2
例如：
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8" /><script> var div = document.getElementById("测试1"); alert(div.id); alert(div.className); alert(div.title);</script><title>测试</title></head><body> <div id="测试1" class="测试2" title="测试3"> <span>0</span> <span>1</span> <span>2</span> <span>3</span> </div></body></html>- 1
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运行时出现如下错误：
问题出在JS运行的时候你的页面还没有加载完成，所以你的JS代码找不到你的页面元素，就会抛出这个问题。解决办法就是把JavaScript代码放在body的最后，例如：
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8" /><title>测试</title></head><body> <div id="测试1" class="测试2" title="测试3"> <span>0</span> <span>1</span> <span>2</span> <span>3</span> </div><script> var div = document.getElementById("测试1"); alert(div.id); alert(div.className); alert(div.title);</script></body></html>- 1
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