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)
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About parameters
##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.
replacement
Required. A string value. Specifies functions for replacing text or generating replacement text.
#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");
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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.
Characters
Replace text
$1,$2,...,$99
Text 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";
});
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运行结果： "bbaa"
b. $的例子
var str = "1234567890";
str.replace( /(\d{3})(\d{3})(\d{4})/g, "$1-$2-$3" );
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运行结果： "123-456-7890"
注： 大多时候是利用regexp和$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')
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//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
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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
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