querySelector和getElementById通過id獲取元素的區別


這是sina同事xiaoniu發現的,如下

<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8"/>
	</head>
	<body>
		<div id="02E503E2A1C011CFC85B7B701A0677EC0900000000000001"></div>
		<script>
			var str = '02E503E2A1C011CFC85B7B701A0677EC0900000000000001';
			function bySelector(id) {
				return document.querySelector('#'+id);
			}
			function byId(id) {
				return document.getElementById(id);
			}

			alert(bySelector(str));
			alert(byId(str));
		</script>
	</body>
</html>

 

兩個函數bySelector,byId分別通過querySelector和getElementById獲取元素。

頁面上有id為“02E503E2A1C011CFC85B7B701A0677EC0900000000000001”的元素。

 

結果:所有支持querySelector的瀏覽器中通過bySelector均獲取不到(報錯),但通過getElementById卻可以獲取。

 

開始懷疑是id的字符串太長的原因導致querySelector獲取不到。真正原因卻是querySelector按css規范實現,即css標識符也不能以數字開頭。

 

W3 寫道

In CSS, identifiers (including element names, classes, and IDs in selectors) can contain only the characters [a-zA-Z0-9] and ISO 10646 characters U+00A0 and higher, plus the hyphen (-) and the underscore (_); they cannot start with a digit, two hyphens, or a hyphen followed by a digit. Identifiers can also contain escaped characters and any ISO 10646 character as a numeric code (see next item). For instance, the identifier "B&W?" may be written as "B\&W\?" or "B\26 W\3F".


相關:

各瀏覽器中querySelector和querySelectorAll的實現差異


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