Response Templating - String Helpers

MockLab provides a set of string manipulation helpers.

Regular expression extract

The regexExtract helper supports extraction of values matching a regular expresson from a string.

A single value can be extracted like this:

{{regexExtract request.body '[A-Z]+'}}"

Regex groups can be used to extract multiple parts into an object for later use (the last parameter is a variable name to which the object will be assigned):

{{regexExtract request.body '([a-z]+)-([A-Z]+)-([0-9]+)' 'parts'}}

String transformation helpers


Use the trim helper to remove whitespace from the start and end of the input:

{{trim request.headers.X-Padded-Header}} // Inline

{{#trim}}                                // Block

    Some stuff with whitespace



abbreviate truncates a string if it is longer than the specified number of characters. Truncated strings will end with a translatable ellipsis sequence (“…”).

For instance the following template:

{{abbreviate 'Mocking APIs helps you develop faster' 21 }} // Mocking APIs helps...


capitalize will make the first letter of each word in the passed string a capital e.g.

{{capitalize 'mock my stuff'}} // Mock My Stuff

capitalizeFirst will capitalise the first character of the value passed e.g.

{{capitalizeFirst 'mock my stuff'}} // Mock my stuff


center centers the value in a field of a given width e.g.

{{center 'hello' size=21}}

will output:


You can also specify the padding character e.g.

{{center 'hello' size=21 pad='#'}}

will output:



cut removes all instances of the parameter from the given string.

{{cut 'mocking, stubbing, faults' ','}} // mocking stubbing faults

Default if empty

defaultIfEmpty outputs the passed value if it is not empty, or the default otherwise e.g.

{{defaultIfEmpty 'my value' 'default'}} // my value

{{defaultIfEmpty '' 'default'}}         // default


join takes a set of parameters or a collection and builds a single string, with each item separated by the specified parameter.

{{join 'Mark' 'Rob' 'Dan' ', '}} // Mark, Rob, Dan

You can optionally specify a prefix and suffix:

{{join 'Mark' 'Rob' 'Dan' ', ' prefix='[' suffix=']'}} // [Mark, Rob, Dan]

Justify left and right

ljust left-aligns the value in a field of a given width, optionally taking a padding character.

{{ljust 'things' size=20}}         // 'things              '
{{ljust 'things' size=20 pad='#'}} // 'things##############'

rjust right-aligns the value in the same manner

{{rjust 'things' size=20}}         // '              things'
{{rjust 'things' size=20 pad='#'}} // '##############things'

Lower and upper case

lower and upper convert the value to all lowercase and all uppercase:

{{lower 'MockLab'}} // mocklab
{{upper 'MockLab'}} // MOCKLAB


replace replaces all occurrences of the specified substring with the replacement value.

{{replace 'the wrong way' 'wrong' 'right' }} // the right way


slugify converts to lowercase, removes non-word characters (alphanumerics and underscores) and converts spaces to hyphens. Also strips leading and trailing whitespace.

{{slugify 'Mock my APIs'}} // mock-my-apis

Strip tags

stripTags strips all [X]HTML tags.

{{stripTags '<greeting>hi</greeting>'}} // hi


substring outputs the portion of a string value between two indices. If only one index is specified the substring between this point and the end will be returned.

{{substring 'one two' 4}}   // two
{{substring 'one two' 0 3}} // one

Word wrap

wordWrap wraps words at specified line length.

{{wordWrap 'one two three' 4}}

will output:



yesno maps values for true, false and optionally null, to the strings “yes”, “no”, “maybe”.

{{yesno true}}   // yes
{{yesno false}}  // no
{{yesno null}}   // maybe

You can also specify different strings to represent each state:

{{yesno true yes='aye'}}    // aye
{{yesno false no='nay'}}    // nay
{{yesno null maybe='meh'}}  // meh