javascript - Can anyone explain the difference between these two regular expressions? -

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/^[a-za-z]+$/

vs 

/[^a-za-z]+$/

the ^ @ start of expression means "anchor @ beginning of string".

the ^ inside character class [] expression means negate.

so /^[a-za-z]$/ matches string consists entirely (from beginning end) of upper case , lower case alphabetic characters, while /[^a-za-z]$/ matches "end of string not consist of alphabetic characters" (for example, numbers @ end of string).

this string       -- matches neither                            (contains non alphabetic, doesn't end in it)  number: 123  -- second expression matches ': 123'                           (string ends in non-alphabetic characters)                    -- first expression matches  'this'                            (string contains alphabetic characters)

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