RegExp() constructor

RegExp 用于创建正则表达式对象,该对象用于将文本与一个模式匹配




new RegExp(pattern[, flags])
RegExp(pattern[, flags])


The text of the regular expression.
As of ES5, this can also be another RegExp object or literal (for the two RegExp constructor notations only). Patterns may include special characters to match a wider range of values than would a literal string. 

If specified, flags is a string that contains the flags to add.

Alternatively, if an object is supplied for the pattern, the flags string will replace any of that object's flags (and lastIndex will be reset to 0) (as of ES2015).

If flags is not specified and a regular expressions object is supplied, that object's flags (and lastIndex value) will be copied over.

flags may contain any combination of the following characters:

g (全局匹配)
Find all matches rather than stopping after the first match.
i (忽略大小写)
If u flag is also enabled, use Unicode case folding.
m (多行匹配)
Treat beginning and end characters (^ and $) as working over multiple lines. In other words, match the beginning or end of each line (delimited by \n or \r), not only the very beginning or end of the whole input string.
s (点号匹配所有字符)
Allows . to match newlines.
u (unicode)
Treat pattern as a sequence of Unicode code points. (See also Binary strings).
y (sticky,粘性匹配)
Matches only from the index indicated by the lastIndex property of this regular expression in the target string. Does not attempt to match from any later indexes.



There are two ways to create a RegExp object: a literal notation and a constructor.

  • The literal notation's parameters are enclosed between slashes and do not use quotation marks.
  • The constructor function's parameters are not enclosed between slashes but do use quotation marks.

The following three expressions create the same regular expression:

new RegExp(/ab+c/, 'i') // literal notation
new RegExp('ab+c', 'i') // constructor

The literal notation results in compilation of the regular expression when the expression is evaluated. Use literal notation when the regular expression will remain constant. For example, if you use literal notation to construct a regular expression used in a loop, the regular expression won't be recompiled on each iteration.

The constructor of the regular expression object—for example, new RegExp('ab+c')—results in runtime compilation of the regular expression. Use the constructor function when you know the regular expression pattern will be changing, or you don't know the pattern and are getting it from another source, such as user input.



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