Use Javascript's match function to extract part of a string

Question

I am a sucker at Regular Expressions, I have learnt a few things about them but I can't get my head around them. There's part of a string that i need to extract from some HTML code but I don't know how to use regular expressions to do it.

I know that str.match() function takes in either a regular expression or a string and returns it. I would like to use this function to extract part of the string.

This is my code:

<img src="images/1.jpg" class="imgs" />
<img src="images/2.jpg" class="imgs" />
<img src="images/3.jpg" class="imgs" />

<script>
    var str = document.getElementsByClassName('imgs');  // str that is being matched
    var re = /^"images/.*"$/;
    var res = str[0].match(re);    // returns undefined is not a function
</script>

The 'images/1.jpg' is from an array that is sequential with the numbers. ie . 'images/1.jpg', 'images/2.jpg'.

I want to extract the "images/(num).jpg", whichever number it may be, i need to extract the "images" with the number. The final result should be "images/(num).jpg".

Is it possible to do it with str.match and regular expressions or some other technique should be used?

webkit · Accepted Answer · 2014-05-27 13:36:53Z

1

if the image will always be a jpg you can do:

<img src="images/1.jpg" class="imgs" />
<img src="images/2.jpg" class="imgs" />
<img src="images/3.jpg" class="imgs" />

<script>
    var str = document.getElementsByClassName('imgs');  // str that is being matched
    var re = /images\/[0-9]+\.jpg/g
    var res = str[0].src.match(re)[0];    
</script>

this will return the string you're looking for.

edited May 27, 2014 at 13:36

answered May 27, 2014 at 12:55

webkit

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7 Comments

Hawk Over a year ago

please explain the answer..I don't get why you did str.match(re)[0].

Dhrubajyoti Gogoi Over a year ago

Since number's are always a part of the file. You may replace * with a +.

webkit Over a year ago

match will give you an array of matches, if there's one match, than [0] will give you it as a string.. with out the [0] you'll get an array with one value

Hawk Over a year ago

it does work..+1 for working..but me code still didn't work how i needed it to

webkit Over a year ago

sure, the reason it's not working is a few errors in your code.. I've edited your above question with comments where I see problems, basically your variable 'str' is returning an array of elements so you can't treat it as string.. you need to grab the src 'str[0].src' as I've written over your example above

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