The first line of code is:
var fieldRegExp = "^[0-9]{4}-[0-9]{3}-[0-9]{3}$"; // nnnn-nnn-nnn
This is a regular expression to describe a pattern of characters: nnnn-nnn-nnn
Where n is a digit from 0 to 9.
Components of the regular expression:
^ indicates the start of the string
[] contains a range of characters, in this case 0 to 9, any of which are valid
{} contains a number that specifies the expected number of the previous item
- is literal, i.e. you are expecting a dash between the groups of numbers
$ indicates the end of the string
The next bit of code is:
if (this.rawValue.search(fieldRegExp) === -1) {
false;
}
else {
true;
}
"search" is a method of the JavaScript String object. The search method searches for a match between a regular expression (in this case: fieldRegExp) and a string (in this case: this.rawValue). The method returns the position of the match or -1 if no match is found.
If the regular expression pattern is contained in this.rawValue, the search method will match it and return its position in the string. In this case, the position would always be 0 because we use ^ to specify that the pattern must be at the start of the string.
If the pattern is not found in this.rawValue then -1 will be returned.
There are plenty of regular expression and JavaScript resources on the web, just do a search. Here's one example for the "search" method: http://www.w3schools.com/jsref/jsref_search.asp
