Uncaught TypeError: Cannot read property 'indexOf' of undefined

[adyoi]

12345
$('.digit').number(true);

Uncaught TypeError: Cannot read property 'indexOf' of undefined
at HTMLSpanElement. (jquery.number.js:567)
at Function.each (jquery.js:367)
at jQuery.fn.init.each (jquery.js:202)
at jQuery.fn.init.$.fn.number (jquery.number.js:558)
at HTMLDocument. (*)
at mightThrow (jquery.js:3557)
at process (jquery.js:3625)

jQuery JavaScript Library v3.4.1
jQuery number plug-in 2.1.5