How To Only Allow Alpha Numeric Chars With JavaScript

You need to make your condition test a regexp, not a string:

if(!/^[a-zA-Z0-9]+$/.test(name)){ ...

meaning:

• ^ -- start of line
• [a-zA-Z0-9]+ -- one or more characters/numbers
• $ -- end of line

or you could search for the inverse of that, which is "any non-accepted character":

if(/[^a-zA-Z0-9]/.test(name)){

if (name.match(/[\W_]/)) { //...

Meaning if the "name" string has any character which is a non-alphanumeric or an underscore then execute the block. Note that we have to separately check for underscore (_) because the alphanumeric character class (\w) includes the underscore (so the negative class (\W) does not).