Same JavaScript function returns random results -

i'm confused:

function is_valid(name) {     var regexp_name = /^(\d|\w)*$/gi;     return regexp_name.test(name); } 

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// console console.log(is_valid("test")); => true  console.log(is_valid("test")); => false  console.log(is_valid("test")); => true  console.log(is_valid("test")); => false 

what doing wrong?

remove /g flag.

the regexp object somehow reused. when /g flag present, regex engine start previous matched location until whole string consumed.

 1st call:       test                  ^  after 1st call: test   (found "test")                      ^  2nd call:       test                      ^  after 2nd call  test   (found nothing, reset)                  ^ 

btw, \w equivalent [0-9a-za-z_] in javascript. therefore, \d| , /i flag redundant. , since you're not using captured group, there's no need keep (…). following enough:

var regexp_name = /^\w*$/;