JS uses the Replace () method and the regular expression to search and replace instances of strings _javascript tips

1, JS string replacement and replace () method of Use

The Replace (Regexp,replacement) method has two parameters, the first parameter can be a plain text string or a RegExp object, see the use of RegExp objects, and the second argument is a string or a function.

Here are some examples of JS string replacements:

Example 1:

Copy Code code as follows:

var str= "Hello world!";
document.write (Str.replace (/world/, "Phper"));

Example 2:

Copy Code code as follows:

var reg=new RegExp ("(\\w+), (\\d+), (\\w+)", "GMI");
var info= "Lili,14,china";
var rep=info.replace (Reg, "She is $ $ years old, come from $");
Alert (rep);

Example 3:

Copy Code code as follows:

var reg=new RegExp ("(\\w+), (\\d+), (\\w+)", "GMI");
var info= "Lili,14,china";
Var name, age, from;
function Prase_info (M,P1,P2,P3) {//can also use non explicit parameters, using arguments to obtain
name = P1;
age = p2;
from = P3;
Return "She's" +p1+ "," +p2+ "years old, come from" +P3;
}
var rep=info.replace (Reg, Prase_info);
Alert (rep);
Aler (name);

2, the use of RegExp objects

JavaScript provides a RegExp object to complete the operation and functionality of regular expressions, and each regular expression pattern corresponds to a regexp instance. There are two ways to create an instance of a RegExp object.

Using the explicit constructor of REGEXP, the syntax is: New REGEXP ("pattern" [, "Flags"]), using the implicit constructor of REGEXP, in plain text format:/pattern/[flags]. The two statements in Example 4 are equivalent.

Example 4:

Copy Code code as follows:

var Re1 = new RegExp ("\\d{5}");
var re2 =/\d{5}/;

3, the search of strings and the use of the Exec () method

The Exec () method returns an array that holds the result of the match. If no match is found, the return value is null.

Example 5:

Copy Code code as follows:

var reg=new RegExp ("(\\w+), (\\d+), (\\w+)", "GMI");
var m=reg.exec ("Lili,14,china");
var s= "";
for (i = 0; i < m.length; i++) {
s = s + m[i] + "\ n";
}
alert (s);

4. Use of test () method

Regexpobject.test (String)

Returns True if string strings contain text that matches regexpobject, or false.

Example 6:

Copy Code code as follows:

var reg=new RegExp ("(\\w+), (\\d+), (\\w+)", "GMI");
var m=reg.test ("Lili,14,china");
alert (regexp.$1);
alert (regexp.$2);
alert (regexp.$3);