Here is how you can convert space to hyphen on a string in JavaScript. The toLowerCase() method will also be added to make all the characters lower case, in case you want the string to be a slug or as part of a url.
Using the replaceAll() method:
let str = "new page Link";
let value = str.replaceAll(" ", "-").toLowerCase();
console.log(value); // new-page-link
Using Regex
let str = "new page Link";
let value = str.replace(/\s+/g, "-").toLowerCase();
console.log(value); // new-page-link
Using the join() method:
let str = "new page Link";
let value = str.split(" ").join("-").toLowerCase();
console.log(value); // new-page-link