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Editorial Team
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Asked: 2026-06-16T21:28:01+00:00

I have an html file myfile.html , which includes a script with a line

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I have an html file myfile.html, which includes a script with a line like this:

var json = '[{"name":"Hydrogen","number":"1","symbol":"H","weight":"1.00794"},{"name":"Helium","number":2,"symbol":"He","weight":4.002602},{"name":"Lithium","number":3,"symbol":"Li","weight":6.941},{"name":"Beryllium","number":4,"symbol":"Be","weight":9.012182},{"name":"Boron","number":5,"symbol":"B","weight":10.811},{"name":"Carbon","number":6,"symbol":"C","weight":12.0107}]';

The string within single quotes that is assigned to variable json will actually vary. I would like to replace this string with the entire contents of another file myjson.json.

I tried with the code here:
Find and replace in a file in Ruby
and here:
search and replace with ruby regex
doing this:

replace = File.read("myjson.json")
changefile = File.read("myfile.html")
changefile.sub( %r{var json = '[^<]+';}, replace )

but its not working. I’m not sure if its the regex I’m doing incorrectly, or if its something more.

UPDATE

After reading the reply below, my first attempt was:

replace = File.read("myjson.json")
changefile = File.read("myfile.html")
changefile.sub!(%r{var json = '.+'}, replace)
puts changefile

This did the find correctly, but removed all of the var json = '' and replaced it with myjson.json – I want to keep var json = and only replace the contents between the two single quotes after. So then I tried:

replace = File.read("myjson.json")
changefile = File.read("myfile.html")
changefile.sub!(%r{var json = '.+'}, "var json = 'replace'")
puts changefile

But that just replaced it with var json = 'replace'

I want to use the original var json = to find the location, but I don’t want it to be removed.

So I did something I know is dumb and wrong, but it worked:

replace = File.read("myjson.json")
changefile = File.read("myfile.html")
changefile.sub!(%r{var json = '.+'}, "var json = 'thanksforthehelptinman'")
changefile.sub!(%r{thanksforthehelptinman}, replace)
puts changefile

Thanks for the help!

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1 Answer

  1. Editorial Team

    The regex isn’t right because [ and ] are reserved in regex. You need to escape them:

    %r{var json = '\[.+\]'}

    I can’t be more exact because I don’t know what’s in your JSON file, but that should get you into the ballpark.

    Also, unless you assign changefile.sub to something, the substitution will be thrown away. You can do one of these two things:

    changefile = changefile.sub(%r{var json = '\[.+\]'}, json)

    or mutate changefile:

    changefile.sub!(%r{var json = '\[.+\]'}, json)
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