Question

How can I out if a string only contains a certain set of characters: { A-Z and } ?

For example

• {VARIABLE} => should return true
• {VARiABLE} => should be false, because there’s a lowercase i inside
• { VARIABLE} => should be false because there’s a space etc.

Oh, very important:

the string MUST have at least one character between { and }, so:

• {} should be false too…

Answer 1

In that case use:

/^{[A-Z]+}$/.test(str);

The regexp represents any string of the format:

• First a {
• Then one or more capital letters
• Then a }

The ^...$ makes sure that the string should be exactly of this form, rather than a substring only (otherwise test{AAA} would match too).