RegEx for matching strings not started with a number passing alphanumeric

Question

I am looking for a regex that only accepts numbers and letters and the first character cannot start with a number.

I found an OK solution that doesn't work all the time by doing:

export const cannotBeginWithAdigit= new RegExp("/^d/");
export const canOnlyContainNumsbersAndDigits = new RegExp('/[,"/\\[]:|<>+=.;?*]/g');

I place the regex between an || to test the first one then the second one.

Other that doesn't work:

^d{1}[0-9a-zA-Z]

Answer 1

Here, we can start (^) our expression with a not-start-with digits ([^\d]) followed by a list of our desired chars:

^[^\d][A-Za-z0-9]+

DEMO

Then, we can also add additional boundaries. For example, anubhava's advice in the comment is good by adding an end char and using i flag:

/^[a-z][a-z\d]*$/i

Test

const regex = /^[^\d][A-Za-z0-9]+/gm;
const str = `123abc
abc123abc
`;
let m;

while ((m = regex.exec(str)) !== null) {
    // This is necessary to avoid infinite loops with zero-width matches
    if (m.index === regex.lastIndex) {
        regex.lastIndex++;
    }
    
    // The result can be accessed through the `m`-variable.
    m.forEach((match, groupIndex) => {
        console.log(`Found match, group ${groupIndex}: ${match}`);
    });
}

RegEx Circuit

jex.im visualizes regular expressions.