Rewriting HTTP url to HTTPS using regular expression and javascript

I'm in a situation where I need to rewrite an url in javascript and switch it from http protocol to https.

I can match https urls with:

if(url.match('^http://')){开发者_JAVA百科

but how do I form the https url using regular expressions and javascript?

url =  "https://" + ?;

---

Replace directly with a regex :

url = url.replace(/^http:\/\//i, 'https://');

---

Cannot it be done by simply replacing the http string?

if(url.match('^http://')){
     url = url.replace("http://","https://")
}

---

Depending on your case, you might prefer to slice:

processed_url = "http" + initial_url.slice(5);

Example of http to https:

var initial_url;
var processed_url;

initial_url = "http://stackoverflow.com/questions/5491196/rewriting-http-url-to-https-using-regular-expression-and-javascript";

processed_url = "https" + initial_url.slice(6);

console.log(processed_url)

Example of https to http:

var initial_url;
var processed_url;

initial_url = "https://stackoverflow.com/questions/5491196/rewriting-http-url-to-https-using-regular-expression-and-javascript";

processed_url = "http" + initial_url.slice(5);

console.log(processed_url)