Javascript str.replace with variables

Question

I have found a short script which finds a line with a certain phrase in it and replaces the whole line with a new line. However I can't work out how to include a variable where it says '#RemoveMe' in the str.replace. (I want to include the variable 'start' which is passed in by the function's trigger, to make --> (/^.start.$/mg, ""))

Any help appreciated...

        var str = 'line1\n'+
          'line2\n'+
          '#RemoveMe line3\n'+
          'line4';

        var test = str.replace(/^.*#RemoveMe.*$/mg, "");

Thanks.

h2ooooooo · Accepted Answer · 2013-10-01 13:14:15Z

6

This is a limitation of the inline regular expression notation.

If you use new RegExp() you can pass the expression as a string.

var find = "start";
var regexp = new RegExp("^.*" + find + ".*$", "mg"); // note: no delimiters
str.replace(regexp, "");

edited Oct 1, 2013 at 13:14

h2ooooooo

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answered Oct 1, 2013 at 13:12

Halcyon

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5 Comments

h2ooooooo Over a year ago

If you need to escape the value (to make sure the user can actually use .'s etc.), you can use PHPJS's version of preg_quote

Halcyon Over a year ago

There is never a (good) reason to allow user input in a regular expression.

John Dvorak Over a year ago

@FritsvanCampen negative. user filtering

Halcyon Over a year ago

You don't need regular expressions for text filtering. Anything more complex is probably silly. Wildcards go a long way.

StorySystems Over a year ago

Thank-you, exact answer and extremely quick! :)

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