insert a variable in a regex _

Question

var adjectives = "blue|pretty|big";
regex = /blue is an adjective/i;

Let's say I need to use the adjectives above multiple times. So, instead of doing:
var chance1 = /(blue|pretty|big) is an adjective/i;
var chance2 = /(blue|pretty|big) is definitely an adjective/i;
var chance3 = /(blue|pretty|big) is adjective/i;

Instead I want to do something like

var chance1 = /(+adjectives+) is an adjective/i;
var chance 2 = /(+adjectives+) is definitely an adjective/i; ...

That's an example.
So, how do we use a variable inside a regex?

Answer 1

That's when the RegExp constructor comes into play:
RegExp (pattern, flags)

E.g:
var adj = "(some|adjetives)";
var re = new RegExp (adj, "i");