JavaScript replace regex

Question

Given this function   function Repeater template         var repeater              markup  template           replace  function pattern  value                this markup   this markup replace pattern  value                          return repeater        How do I make this markup replace   replace globally  Here s the problem  If I use it like this   alert new Repeater   TEST ONE  TEST ONE   replace   TEST ONE    foobar   markup     The alert s value is  foobar  TEST ONE    If I change Repeater to the following  then nothing in replaced in Chrome   function Repeater template         var repeater              markup  template           replace  function pattern  value                this markup   this markup replace new RegExp pattern   gm    value                          return repeater           and the alert is  TEST ONE  TEST ONE

User · Answer

Your regex pattern should have the g modifier:

var pattern = /[somepattern]+/g;

notice the g at the end. it tells the replacer to do a global replace.

Also you dont need to use the RegExp object you can construct your pattern as above. Example pattern:

var pattern = /[0-9a-zA-Z]+/g;

a pattern is always surrounded by / on either side - with modifiers after the final /, the g modifier being the global.

EDIT: Why does it matter if pattern is a variable? In your case it would function like this (notice that pattern is still a variable):

var pattern = /[0-9a-zA-Z]+/g;
repeater.replace(pattern, "1234abc");

But you would need to change your replace function to this:

this.markup = this.markup.replace(pattern, value);

User · Answer

In terms of pattern interpretation  there s no difference between the following forms     pattern  new RegExp  pattern     If you want to replace a literal string using the replace method  I think you can just pass a string instead of a regexp to replace   Otherwise  you d have to escape any regexp special characters in the pattern first - maybe like so   function reEscape s        return s replace                      mg      1               var re   new RegExp reEscape pattern    mg    this markup   this markup replace re  value

User · Answer

You need to double escape any RegExp characters  once for the slash in the string and once for the regexp        TESTONE  TESTONE  replace  new RegExp     TESTONE   gm    foo     Otherwise  it looks for the end of the line and  TESTONE   which it never finds    Personally  I m not a big fan of building regexp s using strings for this reason   The level of escaping that s needed could lead you to drink   I m sure others feel differently though and like drinking when writing regexes

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