javascript - String replace function behavior - error "nothing to repeat"

Question

The below code gives the error:

var a = "hello {0} world";
a.replace(/{0}/g, "little");

But this one works:

var a = "hello {str} world";
a.replace(/{str}/g, "little");

Why do we get this error?

Answer 1

Because {n} (with n being a positive integer) is quantifier syntax, see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions/Quantifiers

You don’t want the curly braces to have their “special meaning” here, but want them treated as plain characters - so you should escape them.

a.replace(/{0}/g,"little")