Question

i dont understand how regex works so this may be is a simple question for many people, but for me is very important that a person can explain me with simple words how can i use this.

i need to validate in jquery adding a new function

$.validator.addMethod("loginRegex",function(a,b){return this.optional(b)||/^[a-zA-Z\d]+$/.test(a)},"Solo se aceptan letras o numeros");

this function accept only letters and numbers, but if you put FH374HD3 the validate return me true, but i need to valid 4 letters and 4 numbers in that order, example: “ABCD4578”, only letters and numbers but 4 letters first and 4 numbers at the end.

is that posible??? tnx all!

Answer 1

This will match a string that is exactly 8 characters long that starts with exactly four letters and is followed by four numbers:

/^[a-z]{4}\d{4}$/i

This could also be written as:

/^[A-Za-z]{4}\d{4}$/

with the case insensitivity placed inline.

• ^ matches the beginning of the string
• [a-z] matches the letters from lower case a to lower case z
• {4} matches the previous selection 4 times ([a-z][a-z][a-z][a-z] but in fewer characters)
• \d matches digits (equivalent to [0-9])
• {4} is as above (\d\d\d\d but in fewer characters)
• $ matches the end of the string
• i is the case-insensitivity flag so that [a-z] matches for capital letters as well.

It should also be noted that this will not match for special characters such as é or à as they are not in the range [a-z].