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Regular Expressions in JavaScript

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Using Regular Expressions in JavaScript

2:33 with Joel Kraft

Learn two common methods in JavaScript that leverage the power of regular expressions: test() and replace().

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    I want to show you how you can use regular expressions in JavaScript. 0:00
    Let's look at two JavaScript methods we'll use to accomplish the behavior you saw 0:04
    in the demo. 0:09
    First, the test method lets you check to see if a string matches the pattern you've 0:10
    defined in a regular expression. 0:14
    To use it, you create a regular expression. 0:17
    Then call the test method while passing the string you wish to check. 0:20
    This is the JavaScript equivalent of typing a regex into the top window of 0:24
    regex pal and a test string into the lower window. 0:29
    This method will return true if the regex matches the string and false if not. 0:33
    To format the telephone number, we'll us replace(). 0:38
    To use replace(), start with a string, call replace() on the string, 0:42
    passing in a regex to match, as well as a replacementString. 0:47
    Replace() will return a newString modified to your specifications. 0:52
    Let's play with the test and replace methods in Chrome's DevTools console. 0:57
    I'll create a new regular expression, 1:02
    this matches corn if it's at the beginning of a string. 1:05
    Now I'll test the string corncob by calling test on the regular expression. 1:08
    Remember test returns a Boolean value, because corncob begins with corn, 1:16
    this evaluates to true. 1:21
    Now I'll test popcorn, this evaluates to false, 1:24
    because even though popcorn contains corn, it is not at the beginning of the string. 1:30
    Now let's use this expression with the replace() method. 1:36
    I'll create the string corndog and store it in a variable string1. 1:40
    Now, let's replace corn with hot. 1:49
    I'll call replace() on string1, passing in the regex and the replacement string. 1:52
    I get the string hotdog back. 2:00
    Now, we'll try replace() on the string popcorn. 2:03
    We'll try to replace it with tart. 2:06
    Again, corn isn't matched, because it isn't at the beginning of the test string. 2:17
    No replacement was made and I got my original string back. 2:22
    In the next video, I wanna show you one more key feature of regular expressions, 2:26
    flags, see you there. 2:31

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