javascript find and replace a dynamic pattern in a string

Question

I have a dynamic pattern that I have been using the code below to find

var matcher = new RegExp("%" + dynamicnumber + ":", "g");
var found = matcher.test(textinput);

I need the pattern to have a new requirement, which is to include an additional trailing 5 characters of either y or n. And then delete it or replace it with a '' (nothing).

I tried this syntax for the pattern, but obviously it does not work.

var matcher = new RegExp("%" + dynamicnumber + ":"  + /([yn]{5})/, "g");

Any tip is appreciated

TIA.

FailedDev · Accepted Answer · 2011-10-16 17:31:35Z

2

You should only pass the regex string into the RegExp c'tor :

var re = new RegExp("%" + number + ":"  + "([yn]{5})", "g");

answered Oct 16, 2011 at 17:31

FailedDev

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2 Comments

Jamex Over a year ago

Thanks Failed, this is exactly what I did last night (or I thought I did), but it did not work. But now I have an alert statement, and it does return the match as 'true', so it does work, but I guess my replace code does not replace.

Jamex Over a year ago

I will try to figure it out first since I now have confirmation that the pattern does work. It is probably something really simple that I missed due to trying to write codes at 2-3am. Thank you for your help.

Amber · Accepted Answer · 2011-10-16 17:30:37Z

2

var matcher = new RegExp("(%" + number + ":)([yn]{5})", "g");

Then replace it with the contents of the first capture group.

answered Oct 16, 2011 at 17:30

Amber

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1 Comment

Jamex Over a year ago

Thanks Amber, I had something similar to yours, and I guess it did work, I just have something else that did not work. Thanks for the help.

Rob W · Accepted Answer · 2011-10-16 17:30:43Z

2

Use quotes instead of slashes:

var matcher = new RegExp("%" + number + ":([yn]{5})", "g");

Also, make sure that dynamicnumber or number are valid RegExps. special characters have to be prefixed by a double slash, \\, a literal double slash has to be written as four slashes: \\\\.

answered Oct 16, 2011 at 17:30

Rob W

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4 Comments

Jamex Over a year ago

Thanks Rob W, I did something similar to this last night, it turns out that it did work, I just have something else that does not work.

Rob W Over a year ago

Regular expressions are converted to strings when they're concanated with a string: "%" + /[yn]{5}/ > "%/[yn]{5}/".

Rob W Over a year ago

@Jamex In your first RegExp, you were using dynamicnumber. In the second RegExp, however, you're using number. Are you sure that this is correct?

Jamex Over a year ago

@Rob W, I just forgot to change the text when I posted, but your suggestion does work. I just need to figure out why I can't replace the pattern in my string, probably something simple. Thanks.

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