How to use regex to substitute a null value located at the end of a string?

edit

Assuming that you want to replace a null value (represented by an empty string or null character) located at the end of a string using regex, you can use the following regular expression pattern:

/(.*?)\0$/

This pattern captures all characters in the string before the null value using a non-greedy wildcard expression (.*?), and uses a dollar sign $ to anchor the null value at the end of the string.

To replace the null value with a new value (e.g. "default"), you can use the following regex substitution in JavaScript:

let str = "hello\0"; // input string with null value at end
let newStr = str.replace(/(.*?)\0$/, "$1default"); // replace null value with "default"
console.log(newStr); // prints "hellodefault"

In this example, the replace() method takes two arguments: the regex pattern and the replacement string. The replacement string uses $1 to reference the captured group (i.e. all characters in the string before the null value), and appends "default" to it. The resulting string is stored in the newStr variable and printed to the console.