JavaScript RegExp \b 和 \B 元字符

2025 年 3 月 18 日 | 6 分钟阅读

正则表达式 "\b" 在 JavaScript 中表示输入字符串的字符可用起始或结束位置。正则表达式 "\B" 表示 JavaScript 输入字符串中字符不可用的起始或结束位置。我们可以测试、搜索和匹配字符串中所需字符的可达性。

语法

JavaScript "\b" 正则语法

该语法用于表示字符串开头的可用字符。

该语法表示字符串结尾的可用字符。

JavaScript "\B" 正则语法

该语法表示字符串开头不可用的字符。

该语法表示字符串结尾不可用的字符。

示例

JavaScript "\b" 正则示例

这些示例显示了字符在字符串开头或结尾的可达性。

示例 1

该示例显示了所需字符在字符串开头的可达性。

<!DOCTYPE html>
<html>
<head>
<title>
JavaScript RegExp \b Metacharacter
</title>
<style>
#demo1{
background-color: orange;
border: 1px solid black;
width: 350px;
}
</style>
</head>
<body>
<div id = "demo1">
<h3>
JavaScript RegExp \b Metacharacter 
</h3>
<h4> The search method with the "g" modifier get the position of the "po" character in the beginning.
</h4>
<div id = "regex_information"> </div>
<!-- click the button to get the output -->
<button onclick = "display();"> Click Here ! </button>
</div>
<script>
//Get the position of the value at the start position
function display() {
let input_pattern = /\bpo/g;
var val1 = 'T point Tech';
var val2 = 'TpointTech';
var val3 = 'java point';
//use regex search method for pattern 
var t1 = val1.search(input_pattern); 
var t2 = val2.search(input_pattern); 
var t3 = val3.search(input_pattern); 
//the output shows the availability of the value 
var ele = document.getElementById("regex_information");
ele.innerHTML = "T point Tech : "+t1+"<br> TpointTech: "+t2+" <br> java point : "+t3;
}
</script>
</body>
</html>

输出

输出显示了开头位置所需的字符。

$JavaScript RegExp \b and \B Metacharacter$

示例 2

该示例显示了所需字符在字符串结尾的可达性。

<!DOCTYPE html>
<html>
<head>
<title>
JavaScript RegExp \b Metacharacter
</title>
<style>
#demo1{
background-color: orange;
border: 1px solid black;
width: 350px;
}
</style>
</head>
<body>
<div id = "demo1">
<h3>
JavaScript RegExp \b Metacharacter 
</h3>
<h4> The search method with the "g" modifier gets the position of the "nt" character in the ending position.
</h4>
<div id = "regex_information"></div>
<!-- click the button to get the output -->
<button onclick = "display();"> Click Here ! </button>
</div>
<script>
//Get the position of the value at the end position
function display() {
let input_pattern = /nt\b/g;
var val1 = 'T point Tech';
var val2 = 'TpointTech';
var val3 = 'java Tpoint';
var t1 = val1.search(input_pattern); 
var t2 = val2.search(input_pattern); 
var t3 = val3.search(input_pattern); 
//the output shows the position of the value 
var ele = document.getElementById("regex_information");
ele.innerHTML = "T point Tech : "+t1+"<br> TpointTech: "+t2+" <br> java Tpoint : "+t3;
}
</script>
</body>
</html>

输出

输出显示了开头位置所需的字符。

$JavaScript RegExp \b and \B Metacharacter$

Example3

该示例测试了所需字符在区分大小写的输入值时在字符串开头的可达性。

<!DOCTYPE html>
<html>
<head>
<title>
JavaScript RegExp \b Metacharacter
</title>
<style>
#demo1{
background-color: orange;
border: 1px solid black;
width: 350px;
}
</style>
</head>
<body>
<div id = "demo1">
<h3>
JavaScript RegExp \b Metacharacter 
</h3>
<h4> The match method with the "g" modifier gets the position of the "java" character not in the beginning.
</h4>
<div id = "regex_information"> </div>
<!-- click the button to get the output -->
<button onclick = "display();"> Click Here! </button>
</div>
<script>
//Get the value using the match method at the start position
function display() {
let input_pattern = /\bjava/g;
var val1 = 'T point Tech';
var val2 = 'TpointTech';
var val3 = 'java point';
//use regex match method for pattern 
var t1 = val1.match(input_pattern); 
var t2 = val2.match(input_pattern); 
var t3 = val3.match(input_pattern); 
//the output shows the position of the value 
var ele = document.getElementById("regex_information");
ele.innerHTML = "T point Tech : "+t1+"<br> TpointTech: "+t2+" <br> java point : "+t3;
}
</script>
</body>
</html>

输出

输出显示了开头位置区分大小写的字符。

$JavaScript RegExp \b and \B Metacharacter$

JavaScript "\B" 正则示例

这些示例显示了字符在字符串开头或结尾的不可达性。

示例 1

该示例显示了字符串开头不存在所需字符。

<!DOCTYPE html>
<html>
<head>
<title>
JavaScript RegExp \B Metacharacter
</title>
<style>
#demo1{
background-color: orange;
border: 1px solid black;
width: 350px;
}
</style>
</head>
<body>
<div id = "demo1">
<h3>
JavaScript RegExp \B Metacharacter 
</h3>
<h4> The search method with the "g" modifier gets the position of the "va" character, not in the ending position.
</h4>
<div id = "regex_information"></div>
<!-- click the button to get the output -->
<button onclick = "display();"> Click Here ! </button>
</div>
<script>
function display() {
// use not available po value at the start of the position
let input_pattern = /\Bpo/g;
var val1 = 'T point Tech';
var val2 = 'TpointTech';
var val3 = 'java point';
//use the search method for the input pattern 
var t1 = val1.search(input_pattern); 
var t2 = val2.search(input_pattern); 
var t3 = val3.search(input_pattern); 
//the output shows the not available position of the value 
var ele = document.getElementById("regex_information");
ele.innerHTML = "T point Tech : "+t1+"<br> TpointTech: "+t2+" <br> java point : "+t3;
}
</script>
</body>
</html>

输出

输出显示了开头位置不存在的所需字符。

$JavaScript RegExp \b and \B Metacharacter$

示例 2

该示例显示了字符串结尾不存在的所需字符。我们可以获取正则表达式或所需字符来搜索结尾位置。

<!DOCTYPE html>
<html>
<head>
<title>
JavaScript RegExp \B Metacharacter
</title>
<style>
#demo1{
background-color: orange;
border: 1px solid black;
width: 350px;
}
</style>
</head>
<body>
<div id = "demo1">
<h3>
JavaScript RegExp \B Metacharacter 
</h3>
<h4> The search method with the "g" modifier gets the position of the "va" character, not in the ending position.
</h4>
<div id = "regex_information"></div>
<!-- click the button to get the output -->
<button onclick = "display();"> Click Here ! </button>
</div>
<script>
function display() {
// use not available va value at the end of the position
let input_pattern = /va\B/g;
var val1 = 'T point Tech';
var val2 = 'TpointTech';
var val3 = 'java point';
//use the search method for the input pattern 
var t1 = val1.search(input_pattern); 
var t2 = val2.search(input_pattern); 
var t3 = val3.search(input_pattern); 
//the output shows not available end position of the value 
var ele = document.getElementById("regex_information");
ele.innerHTML = "T point Tech : "+t1+"<br> TpointTech: "+t2+" <br> java point : "+t3;
}
</script>
</body>
</html>

输出

输出显示了结尾位置不存在的所需字符。

$JavaScript RegExp \b and \B Metacharacter$

Example3

该示例测试了区分大小写的输入值时，字符串开头不存在所需字符。小写数据不会测试字符串中的大写字符。

<!DOCTYPE html>
<html>
<head>
<title>
JavaScript RegExp \B Metacharacter
</title>
<style>
#demo1{
background-color: orange;
border: 1px solid black;
width: 350px;
}
</style>
</head>
<body>
<div id = "demo1">
<h3>
JavaScript RegExp \B Metacharacter 
</h3>
<h4> The match method with the "g" modifier gets the position of the "java" character not in the beginning.
</h4>
<div id = "regex_information"></div>
<!-- click the button to get the output -->
<button onclick = "display();"> Click Here ! </button>
</div>
<script>
function display() {
// use not available java value at the start of the position
let input_pattern = /\Bjava/g;
var val1 = 'T point Tech';
var val2 = 'TpointTech';
var val3 = 'java point';
//use the match method for the input pattern 
var t1 = val1.match(input_pattern); 
var t2 = val2.match(input_pattern); 
var t3 = val3.match(input_pattern); 
//the output shows a null value 
var ele = document.getElementById("regex_information");
ele.innerHTML = "T point Tech : "+t1+"<br> TpointTech: "+t2+" <br> java point : "+t3;
}
</script>
</body>
</html>

输出

输出显示了开头位置区分大小写的字符。

$JavaScript RegExp \b and \B Metacharacter$

结论

正则表达式的 "\b" 和 "\B" 元字符显示了值的起始和结束位置。

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JavaScript RegExp \b 和 \B 元字符

语法

示例

JavaScript "\b" 正则示例

JavaScript "\B" 正则示例

结论

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JavaScript RegExp \b 和 \B 元字符

语法

示例

JavaScript "\b" 正则示例

JavaScript "\B" 正则示例

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