Javascript: How to have value in string represented by %s and then replaced with a value

Question

I know this a really stupid question.

I've had a good few years experience with javascript but this one thing seems to have skipped my mind, my head has gone blank and I can't remember what it's called and how I would go about doing it.

Basically what I'm looking for is when you have a string variable such as:

var error_message = "An account already exists with the email: %s"

And you then pass a string somehow into this and it replaces the %s.

I probably sound really idiotic, but I'd really appreciate the help / reminding!

Thanks guys.

Answer 1

You just use the replace method:

error_message = error_message.replace('%s', email);

This will only replace the first occurance, if you want to replace multiple occurances, you use a regular expression so that you can specify the global (g) flag:

error_message = error_message.replace(/%s/g, email);

Answer 2

'Modern' ES6 solution: use template literals. Note the backticks!

var email = '[email protected]';
var error_message = `An account already exists with the email: ${email}`;

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Template_literals