Help with script in flow designer: Fetching a number from sys_user and adding 1

[MarinaN]

I need to query sys_user, where a custom string field u_g_number is located. This has a format of "G"+5 digits. 

I need to get the 5 digits, treat them as a number and add 1. This script is my script:

var maxNum = 0; // keep track of the highest numeric value found

var gr = new GlideRecord('sys_user'); // gr on sys_user
gr.orderByDesc('u_g_number');
gr.setLimit(1);
gr.query();


if (gr.next()) { // move to the first record if one exists
    var raw = (gr.u_g_number + '').trim(); // read number, remove space (not really needed but just to be safe)
    var match = raw.match(/^G(\d+)$/i);    // capture all digits after g
    if (match) {                          
        maxNum = parseInt(match[1], 10);   // convert the captured digits to a number
    }
}

var nextNum = maxNum + 1; // add 1 to the largest found number to get the next one
var nextG = 'G' + nextNum; 

gs.log('Flow generated next u_g_number: ' + nextG, 'UGen');
return nextG; 

No number is being generated, any idea why? 

I have an action "create user record" and next to the field u_g_number i added this script (works for another script above where we generate the email)

[Martin Virag]

okay, there are several issues with this script (I would not even use a script its a simple lookup step and then you can use a flow variable to do your operation) , however by fixing your script:
I assume the G is always the beginning in this way its perfectly fine to just use 
the .slice() https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/slice

Other reference is here: https://www.geeksforgeeks.org/javascript/delete-first-character-of-a-string-in-javascript/

Then use the parseInt to make it a number

Finally add +1

Here is the code:

var gr = new GlideRecord('sys_user');
gr.orderByDesc('u_g_number');
gr.setLimit(1);
gr.query();

var nextG;
if (gr.next()) {
    var num = parseInt(gr.u_g_number.slice(1), 10);
    nextG = 'G' + (num + 1);
}

gs.log('Flow generated next u_g_number: ' + nextG, 'UGen');
return nextG;

[Ankur Bawiskar]

@MarinaN 

try this

var maxNum = 0;
var gr = new GlideRecord('sys_user');
gr.addQuery('u_g_number', 'STARTSWITH', 'G');
gr.query();
while (gr.next()) {
    var raw = (gr.getValue('u_g_number') + '').trim();
    var match = raw.match(/^G(\d{5})$/); // captures exactly 5 digits
    if (match) {
        var num = parseInt(match[1], 10);
        if (num > maxNum) maxNum = num;
    }
}
var nextNum = maxNum + 1;
var nextG = 'G' + ('00000' + nextNum).slice(-5); // pads leading zeroes if needed
gs.log('Flow generated next u_g_number: ' + nextG, 'UGen');
return nextG;

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[MarinaN · Accepted solution]

There was no issue with my code - BUT:

Since I am looking through the sys_user table I needed to run the flow as "system user"!

It works now