Question:

Describe what regular expression boundary matches are and give detailed explanations of the boundary matches available in JavaScript Regular Expressions.

There are several commonly used boundaries used in regex. You can think of them as fences show where a pattern can start searching.

• ^

This symbol allows us to start searching at the start of an input or the start of the line if the m charater is used.

  var pattern = /^cat/;

   'the dogcat and the cat' 
  // will match cat but not the cat in dogcat

• $

  This symbol allows us to search at the end of a input of line if the m character is used.

  var pattern = /cat$/;

   'the dogcat and the cat' 
  // will match cat because it is the at the end of the string 

Both these symbols are referred to as anchors and we can use them together to only return a string that has what where looking for.

  var pattern = /^cat$/;

   'the dogcat and the cat' 
  // will not return anything as contains more than just cat
  
  'cat'
  // will be a match as it's only cat 

• \b

This is what we call a word boundary which means a space, tab, caret followed by a word charater will be matched.

  var pattern = /\bwonder/g; 

  'wonder wonder whats in a wonder ball'

  //matches all the words that are wonder 

• \B

This is what we call a non word boundary which means that any character that that is followed by another charter will return a match

  var pattern = /\Bman/; 

  'batman'

  //will match man as it is followed by a character