Note that the expression above will also match 0 Edit with Regexity. We can do this by placing a zero-or-one quantifier (written as ? Edit with Regexity) behind the square brackets: /100 | ? \d / Edit with Regexity However, a more compact way of doing this is to simply make the first character in the two-digit expression optional. One way to do this is to add another digit character \d Edit with Regexity separated by an OR character | Edit with Regexity: /100 | \d | \d / Edit with Regexity Next, we need to deal with the single-digit numbers. The square brackets indicate that we will accept any digit from 1 to 9. However, if we want to match two-digit numbers with no leading zeros, we can change the first digit symbol to a range from 1 to 9 in square brackets: /100 | \d / Edit with Regexity In some instances, you might want to allow this, as many programming languages will automatically drop the leading zero when converting the string to an integer. Note that the two digit characters \d \d Edit with Regexity will also match single digits with a leading zero, such as 01 Edit with Regexity or 08 Edit with Regexity. The double-digit expression is separated from the triple-digit expression using the OR symbol | Edit with Regexity or pipe character, to indicate that we will allow matching either one or the other. Next, we add an expression that will match the double digits, consisting of two digit characters \d Edit with Regexity which will each match any digit from 0 to 9: /100 | \d \d / Edit with Regexity The regular expression above will match exactly 100 Edit with Regexity. In this case, the only triple-digit number that we will allow is 100 Edit with Regexity, since that is the maximum age in our range: /100/ We need to split our regex into two parts, one of which will match single digits and double digits, and another which will match triple digits. Let’s break down how this works: Age Range 0 to 100
It must be able to match single digits (1 to 9), double digits (10 to 99) and certain triple digits (depending on the maximum allowable age).Īn expression that will match ages in the range 0 to 100 is: / ^100 | ? \d $ / Edit with Regexity But regular expressions is another alternative for this.Ī regular expression that validates an age in a specific age range must check that only digits are entered. The validity of this input can usually be checked by comparing the numeric value of the text entered. Users are often required to enter their ages into online forms.
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