Usage examples of replace() method in Javascript

In our daily development, the replace method in javascript belongs to the String object and can be used to replace strings. Replace can also be used in regular expressions, so today we will discuss in detail the use examples of the replace() method in Javascript!

About the definition

The replace() method is used to replace some characters with other characters in a string, or to replace a substring that matches a regular expression.

About syntax

stringObject.replace(regexp/substr,replacement)

About parameters

replacementRequired. A string value. Specifies functions for replacing text or generating replacement text.

##Parameters	Description
##regexp/substr	Required. A RegExp object that specifies the substring or pattern to be replaced. Note that if the value is a string, it is retrieved as a literal literal pattern rather than first being converted to a RegExp object.

#1. The first parameter regexp/substr, when using regular expressions, uses the global identifier g, which can replace all matching substrings, otherwise it will only match once.

For example:

var str = "aaaaa"; 
var str1 = str.replace("a", "b");
var str2 = str.replace(/a/g, "b");

Running results: str1 -> "baaaa", str2 -> "bbbbb"

2. The second parameter replacement can be a character A string or function, or a specific meaning of the $ character.

CharactersReplace text$1,$2,...,$99Text matching the 1st to 99th subexpressions in regexp. $&The substring that matches regexp. $`The text to the left of the matched substring. $'The text to the right of the matched substring. $$Direct quantity symbol.

   

a. function的例子:

var str = "111222aa";
str.replace(/(\d{3})/g, function(word){
 return "b";
});

     运行结果： "bbaa"

    b. $的例子

var str = "1234567890";
str.replace( /(\d{3})(\d{3})(\d{4})/g, "$1-$2-$3" );

     运行结果： "123-456-7890"

注： 大多时候是利用regexp和$的结合来实现需求，所以知道一些基本的正则表达式规则是有必要的。

字符串替换字符串

'I am loser!'.replace('loser','hero')

//I am hero!
直接使用字符串能让自己从loser变成hero，但是如果有2个loser就不能一起变成hero了。

'I am loser,You are loser'.replace('loser','hero');
//I am hero,You are loser

正则表达式替换为字符串

'I am loser,You are loser'.replace(/loser/g,'hero')
//I am hero,You are hero

使用正则表达式，并将正则的global属性改为true则可以让所有loser都变为hero

有趣的替换字符

replaceValue可以是字符串。如果字符串中有几个特定字符的话，会被转换为特定字符串。

字符 替换文本
$& 与正则相匹配的字符串
$` 匹配字符串左边的字符
$' 匹配字符串右边的字符
$1,$2,$,3,…,$n 匹配结果中对应的分组匹配结果
使用$&字符给匹配字符加大括号

var sStr='讨论一下正则表达式中的replace的用法';
sStr.replace(/正则表达式/,'{$&}');
//讨论一下{正则表达式}中的replace的用法
使用$`和$'字符替换内容

'abc'.replace(/b/,"$`");
//aac
'abc'.replace(/b/,"$'");
//acc

使用分组匹配组合新的字符串

'nimojs@126.com'.replace(/(.+)(@)(.*)/,"$2$1")
//@nimojs
replaceValue参数可以是一个函数

StringObject.replace(searchValue,replaceValue)中的replaceValue可以是一个函数.
如果replaceValue是一个函数的话那么，这个函数的arguments会有n+3个参数（n为正则匹配到的次数）

先看例子帮助理解：

function logArguments(){ 
 console.log(arguments);
//["nimojs@126.com", "nimojs", "@", "126.com", 0, "nimojs@126.com"] 
 return '返回值会替换掉匹配到的目标'
}
console.log(
 'nimojs@126.com'.replace(/(.+)(@)(.*)/,logArguments)
)

参数分别为

匹配到的字符串（此例为nimojs@126.com,推荐修改上面代码的正则来查看匹配到的字符帮助理解)
如果正则使用了分组匹配就为多个否则无此参数。（此例的参数就分别为”nimojs”, “@”, “126.com”。推荐修改正则为/nimo/查看控制台中返回的arguments值）
匹配字符串的对应索引位置（此例为0）
原始字符串(此例为nimojs@126.com)
使用自定义函数将A-G字符串改为小写

'JAVASCRIPT'.replace(/[A-G]/g,function(){
 return arguments[0].toLowerCase();
})
//JaVaScRIPT

使用自定义函数做回调式替换将行内样式中的单引号删除

&#39;<span style="font-family:\&#39;微软雅黑\&#39;;">demo</span>&#39;.replace(/\&#39;[^&#39;]+\&#39;/g,function(){  
 var sResult=arguments[0];
 console.log(sResult);//&#39;微软雅黑&#39;
 sResult=sResult.replace(/\&#39;/g,&#39;&#39;);
 console.log(sResult);
//微软雅黑
 return sResult;
})
//<span style="font-family:微软雅黑;">demo</span>

总结：

相信小伙伴们通过对本文的学习和了解，对Javascript中replace()方法的使用有了进一步的了解，希望对你的工作有所帮助！

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