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Using regular expressions in JavaScript



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Link for slides, code samples and text version of the video
http://csharp-video-tutorials.blogspot.com/2015/01/using-regular-expressions-in-javascript.html

What is a Regular Expression
A regular expression is a sequence of characters that forms a search pattern.

Let us understand the use of regular expressions with an example. The following strings contain words and numbers. From the string we want to extract all the numbers. Bsically the program should work with any string.

Mark-9 Tim-890 Sam-10 Sara-9902
Result : 9, 890, 10, 9902

908ABC12XYZ34
Result : 908, 12, 34

$1 $2 $901 ABC(100)
Result : 1, 2, 901, 100

Here is what we want the page to do
1. User enters the string in the first textbox
2. When “Process String” button is clicked, the numbers should be extracted from the string and displayed in the text area element.

It will be very complex and error prone if we have to achieve this without using regular expressions.

[input type=”text” id=”txtBox” style=”width:250px” /]
[br /][br /]
[input type=”button” value=”Process String” onclick=”processString()” style=”width:250px” /]
[br /][br /]
[textarea id=”txtArea” rows=”4″ cols=”30″][/textarea]
[script type=”text/javascript”]
function processString()
{
// Clear the textarea element
document.getElementById(“txtArea”).value = “”;
// Retrieve the user intput from the textbox
var inputString = document.getElementById(“txtBox”).value;
// Regular expression should be in 2 forward slashes //
// Letter g at the end of the regular expression performs a global match
// match() method returns all substrings that match the given regular expression
var result = inputString.match(/d+/g);

if (result != null) {
// Add the retrieved numbers to the textarea element
for (var i = 0; i [ result.length; i++) {
document.getElementById(“txtArea”).value += result[i] + “rn”;
}
}
}
[/script]

Original source

d4mer

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23 responses to “Using regular expressions in JavaScript”

  1. You have the best tutorials on internet, by far. I am so thankful to you, I got my first job due to your SQL tutorials, second job due to your C# tutorials and now I'm using this on my third job. Thank you very much sir.

  15. You don't need to add this line document.getElementById("txtArea").value = ""; . Just write like this document.getElementById("txtArea").value = result[i] + "rn"; without +

  17. AND THAT MY FRIENDS IS WHY I USE PROCESSING AND NOT JSCRIPT OR ORACLE JAVA! SEARCH PATTER HA SEARCH PATTERN IS THE DIRECTIONS A PLANE OR A DIVER OR ABOAT TAKES TO FIND SOMETHING ! REALLY BAD ANALOGY ! REGEX SEARCHES A PAGE FOR CHARACTERS U WANT TO FIND. LIKE A WORD SEARCH !

  18. Hello from South Africa. Your videos are excellent. Better than any video tutorials I have watched. I love that you build up your explanation from start to finish. Thank you very much for your contributions.

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