To check if a string starts with a number in Node.js, you can use a regular expression. 

Here's an example code snippet that checks if a string starts with a number:

const myString = "5abc";
const startsWithNumber = /^\d/.test(myString);

console.log(startsWithNumber); // true

In the code above, we first define a string `myString` that starts with the number 5. We then create a regular expression `/^\d/` that matches any string that starts with a digit (`\d`). 

The `test()` method of the regular expression object is then used to test if `myString` starts with a number. This method returns a boolean value indicating whether the string matches the regular expression or not. 

The result is then logged to the console, which should output `true` since `myString` starts with a number.