Javascript get string between two strings

Question

I like to fetch the values between two string. this is what I am using as a placeholder to change the stuff between. so basically I appended these custom [[num}] to each tag. Im trying to make a database of it. then I am trying to make custom/predefined edits of it base on certain parameters. so basically, if there is a way to get/change/remove the things inside of the open and close strings.

<script>
var num = 14;
</script>

HTML

[[14}]<img width="50" height="50" src="//cdn.com/img5.jpg" alt="comment-image">[{14]] [[15}]<img width="50" height="50" src="//cdn.com/img6.jpg" alt="comment-image">[{15]]

Can’t you just use an array of DOM nodes? Or use a data-num attribute, then select by document.querySelector(`[data-num='${num}']`)? — Sebastian Simon
– Sebastian Simon, Commented Jan 30, 2018 at 3:43
not applicable, I need to update or change or remove the entire thing if need be. — Boy
– Boy, Commented Jan 30, 2018 at 3:52
Why not Xufox's suggestion, except use a <span> wrapper with the data-num as its id? Otherwise, it might help if you be more specific in your question. — Jeff Matthews
– Jeff Matthews, Commented Jan 30, 2018 at 3:55

sorak · Accepted Answer · 2018-01-30 04:23:53Z

1

Here's a javascript function to extract the substring by label number:

function extractField(str, num) {
    var startLabel = '[['+num+'}]';
    return str.substring(str.indexOf(startLabel)+startLabel.length, str.indexOf('[{'+num+']]'));
}

It works by finding the index of the starting label, adding the length of the label string, and then extracting everything up to the ending label.

Example usage:

str='[[14}]<img width="50" height="50" src="//cdn.com/img5.jpg" alt="comment-image">[{14]] [[15}]<img width="50" height="50" src="//cdn.com/img6.jpg" alt="comment-image">[{15]]';

extractField(str, 14);
"<img width="50" height="50" src="//cdn.com/img5.jpg" alt="comment-image">"

answered Jan 30, 2018 at 4:23

sorak

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3 Comments

Boy Over a year ago

thanks it works, is there a way to make this to update the content inside?

sorak Over a year ago

You'll need to have a different function that takes a third argument of a replacement string, and returns something like: str.substring(0, str.indexOf(startlabel))+replacement+str.substring(str.indexOf('[{'+num+']]'), str.length-1)

Boy Over a year ago

Did it like you said but updated. str.substring(0, str.indexOf(startLabel))+startLabel+replacement+str.substring(str.indexOf('[{'+num+']]'), str.length-1)

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