6.470 Regular Expressions

This lesson will teach regular expressions.

The Big Picture:

Regular expressions are good for parsing and validating strings.
Regular expressions are supported in most programming languages.
Reference
- JavaScript Regular Expressions
- PHP Regular Expressions

JavaScript Syntax

Here's an example of the JavaScript syntax for regular expressions:

var a = "hello@mit.edu"

var re = /(\w+)@(\w+)\.edu/

var m = a.match(re)
if (m) {
    print("username: " + m[1])
    print("school: " + m[2])
} else {
    print("didn't match")
}

Regex Example

input: http://www.databasebasketball.com/players/playerlist.htm

regex:

var a = input.match(/<td><a href="playerpage\.htm\?ilkid=\w+ ">[^<]+<\/a><br>/g)
for (var i = 0; i < a.length; i++) {
    var b = a[i]
    b = b.match(/<td><a href="playerpage\.htm\?ilkid=\w+ ">([^<]+)<\/a><br>/)
    b = b[1]
    b = b.replace(/&nbsp;/, " ")
    b = b.match(/([^,]+), (.*)/)
    print(b[2] + " " + b[1])
}

output:

Alaa Abdelnaby
Mahmo Abdul-rauf
Tariq Abdul-wahad
Tom Abernethy
John Abramovic
Alex Acker
Donald Ackerman
...