Custom Regex using Variable

[michaelnicol]

I am working on a program that requires me to use a variable in the regex.

The idea is of follows:

let l1 = "A"
let l2 = "B"
let reg = `/(${l1}|${l2})/`
let regex = new RegExp(reg, 'i')
console.log(regex.test("A"))

I can put any value for l1 and l2 and be able to make a regex that can test for those letters. However, this always returns false.

[danfly09]

The regex built with the assignment operator, do not allow variables.
The regex built with the constructor do allow them.

Instead of declaring a literal reg… Make a string, your string can be built with variables, then use the RegExp constructor and pass the string

> let l1 = 'A'
> let l2 = 'B'
> let str = l1 + '|' + l2
> let reg = new RegExp(str)
> reg.test('A')
true