String Replace Helper for Dust.js

Recently, I’ve been learning about the LinkedIn fork of Dust – a client-side templating solution. Dust allows you to create helpers, which are functions that can be called from within a rendering template. They help separate presentation from logic, which is always a good practice.

Today we created a String Replace helper, which seems like it might be pretty useful for others, so I thought I’d share it.

Following is an example of the helper in use. In this example, the replace helper will replace all instances of a period character with a hyphen in the given message string, and then it will write the trimmed result.

Usage example:

{@replace str="{message}" search="." replace="-" trim="true" /}

Here is the Replace Helper for Dust (also on GitHub Gist)

(function (dust) {
 
 /**
  * Polyfill to create String.trim() if it's not natively available
  */
 if (!String.prototype.trim) {
     (function(){
         // Make sure we trim BOM and NBSP
         var rtrim = /^[\\s\\uFEFF\\xA0]+|[\\s\\uFEFF\\xA0]+$/g;
         String.prototype.trim = function () {
             return this.replace(rtrim, "");
         }
     })();
 }

 /**
  * Processes the given string to escape special meta characters used within
  * Regular Expressions. This is used by the replace helper.
  */
 function escapeRegExp(string) {
     return string.replace(/([.*+?^=!:$\{\}()|\\[\\]\\/\\\\])/g, "\\\\$1");
 }

 /**
  * Performs a global search and replace within a string.
  * In the following example, we replace all periods in the
  * message string with dashes and we trim the result.
  *
  * {@replace str="{message}" search="." replace="-" trim="true" /}
  *
  * str - the input string within which the search and replace will be performed
  * search - the character or sequence to search
  * replace - the character or sequence used to replace
  * trim - when 'true', will trim the string before returning result.
  *
  */
 dust.helpers.replace = function (chunk, ctx, bodies, params) {

     var str = dust.helpers.tap(params.str, chunk, ctx);
     var search = dust.helpers.tap(params.search, chunk, ctx);
     var replace = dust.helpers.tap(params.replace, chunk, ctx);
     var trim = dust.helpers.tap(params.trim, chunk, ctx);

     if(trim && trim == 'true') {
         str = str.trim();
     }

     var result = str.replace(new RegExp(escapeRegExp(search), 'g'), replace);

     return chunk.write( result );

 }

})(typeof exports !== 'undefined' ? module.exports = require('dustjs-linkedin') : dust);