JavaScript String indexOf()用法及代碼示例

字符串 indexOf() 方法

indexOf() is method 是一個 String 方法，用於檢查給定字符串中是否存在子字符串。它從子字符串所在的字符串返回子字符串的起始索引。如果字符串中不存在子字符串 – 則返回 -1。

用法:

    String.indexOf(substring, [offset]);

這裏，substring是要搜索的字符串的一部分，並且[offset]是我們要搜索子字符串的特定索引，它是一個可選參數，默認值為 0。

例：

<html>
<head>
<title>JavaScipt Example</title>
</head>

<body>
<script>		
	var str = "IncludeHelp is for programmers";
	
	var substr = "is";		
	var index = str.indexOf(substr);
	if(index!=-1)
		document.write(substr + " found at " + index + " position.<br>");
	else
		document.write(substr + " does not exist in the " + str + ".<br>");

	substr = "Hello";
	index = str.indexOf(substr);		
	if(index!=-1)
		document.write(substr + " found at " + index + " position.<br>");
	else
		document.write(substr + " does not exist in the " + str + ".<br>");
	
	//searching from a specific index
	substr = "is";
	index = str.indexOf(substr,10);		
	if(index!=-1)
		document.write(substr + " found at " + index + " position.<br>");
	else
		document.write(substr + " does not exist in the " + str + ".<br>");		

	substr = "is";
	index = str.indexOf(substr,20);		
	if(index!=-1)
		document.write(substr + " found at " + index + " position.<br>");
	else
		document.write(substr + " does not exist in the " + str + ".<br>");					
</script>
</body>
</html>

輸出

is found at 12 position.
Hello does not exist in the IncludeHelp is for programmers.
is found at 12 position.
is does not exist in the IncludeHelp is for programmers.

相關用法

注：本文由純淨天空篩選整理自 String indexOf() Method with Example in JavaScript。非經特殊聲明，原始代碼版權歸原作者所有，本譯文未經允許或授權，請勿轉載或複製。