regex - JavaScript RegExp Differences -

what difference between

var regex = /\d/; 

and

var regex = new regex("\d"); 

bob

both evaluate same exact regex, first literal, meaning cannot use variables inside it, cannot dynamically generate regex.

the second uses constructor explicitly , can used create dynamic regular expressions.

var x = '3', r = ( new regexp( x + '\d' ) ); r.test('3d') 

the above example of dynamically constructing regex constructor, can not in literal form.

in 99% of cases rely on first version ( literal ) regexpes in js. in advanced scenario need say, user input dynamically construct regex that's when you'll need second form.

edit #1: the first matches digit, second matches letter d. have double-escape second 1 in order equal first one, assume meant do. remember advice typed above accurate if second example new regexp('\d').

/\d/.test('3') // true ( new regexp('\d') ).test('3') // false ( new regexp('\\d') ).test('3') // true