Match only unicode letters

Starting with ECMAScript 2018, JavaScript finally supports Unicode property escapes natively.

For older versions, you either need to define all the relevant Unicode ranges yourself. Or you can use Steven Levithan's XRegExp package with Unicode add-ons and utilize its Unicode property shortcuts:

var regex = new XRegExp("^\\p{L}*$")
var a = "abcäöüéèê"
if (regex.test(a)) {
    // Match
} else {
    // No Match
}

If you are willing to use Babel to build your javascript then there's a babel-plugin I have released which will transform regular expressions like /^\p{L}+$/ or /\p{^White_Space}/ into a regular expression that browsers will understand.

This is the project page: https://github.com/danielberndt/babel-plugin-utf-8-regex