Detect if string contains numbers only

[Kaptea]

Hello,

I am receiving a string value in power automate that is a phone number from a field in a ms form, the issue i am facing is some people are inputting stuff like "n/a", "opt out", "email addresses", even their names to a clearly marked telephone Number field, my question is how can i check that the string received in power automate only contains numbers 0 to 9 and the + sign. have been looking for a solution for this for a while so any help would be great.

[ekarim2020 · Accepted solution]

Hi @Kaptea ,

There is an isInt() function, but this will not work for you as you need to also accept the + (plus) and may be the space character in the phone number string.

I present one method below. The flow examines each character of the phone number for a valid character (valid characters are 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, +, and space). For each character of the phone number, the flow will record a value of true for a valid phone number character, and false for an invalid character. If this list of true/false values contains a false value  then the phone number string is not a valid phone number.

These are the actions of the flow:

 

The varValidChars contains a list of valid characters that make up a phone number:

[
  "+",
  " ",
  "0",
  "1",
  "2",
  "3",
  "4",
  "5",
  "6",
  "7",
  "8",
  "9"
]

Using the SELECT action: we examine each character of the phone number, and record true (for a valid phone number character) or false (for an invalid character):

*FROM:
range(0, length(variables('varPhoneNumber')))

*MAP:
if(contains(variables('varValidChars'), slice(variables('varPhoneNumber'), item(), add(item(), 1))), true, false)

 

If the output of the SELECT action contains a false value (i.e any invalid character) then this is not a phone number.

 

 

You could further improve the flow further by checking if the phone string starts with a + or a number, that it is of a certain length etc.  

See: How to Extract Numbers from a String Using Power Automate

Hope this helps.

 
Ellis
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[Kaptea]

This is a great solution, thanks @ekarim2020 .

[zz7]

The solution from ekarim2020 using the Select function did not work for me. When I was entering the formula into the Map field of the Select function, I got an error saying that it was not valid JSON.
After a lot of searching, I found a solution that did work (see the reply from grantjenkins that starts with "Another option is to convert your variable to XML".
Link: https://powerusers.microsoft.com/t5/Building-Flows/Checking-string-value-for-Letters/m-p/1927095/hig...