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Defining Regular Expressions some tips....


gogoily

Guys, I've got this document today and post here to share with you. I hope it is helpful to you.


In JavaScript, regular expressions are represented by RegExp objects. RegExp objects may be created with the RegExp( ) constructor, of course, but they are more often created using a special literal syntax. Just as string literals are specified as characters within quotation marks, regular expression literals are specified as characters within a pair of slash (/) characters. Thus, your JavaScript code may contain lines like this: var pattern = /s$/; This line creates a new RegExp object and assigns it to the variable pattern. This particular RegExp object matches any string that ends with the letter "s." (I'll get into the grammar for defining patterns shortly.) This regular expression could have equivalently been defined with the RegExp( ) constructor like this: var pattern = new RegExp("s$"); Creating a RegExp object, either literally or with the RegExp( ) constructor, is the easy part. The more difficult task is describing the desired pattern of characters using regular expression syntax. JavaScript adopts a fairly complete subset of the regular-expression syntax used by Perl, so if you are an experienced Perl programmer, you already know how to describe patterns in JavaScript. Regular-expression pattern specifications consist of a series of characters. Most characters, including all alphanumeric characters, simply describe characters to be matched literally. Thus, the regular expression /java/ matches any string that contains the substring "java". Other characters in regular expressions are not matched literally but have special significance. For example, the regular expression /s$/ contains two characters. The first, "s", matches itself literally. The second, "$", is a special metacharacter that matches the end of a string. Thus, this regular expression matches any string that contains the letter "s" as its last character.


Notice from jlhaslip:
added quote tags. DO NOT cut and paste



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