[Solved] Check if input field can only consist of lower and uppercase letters, numbers and the characters . and _

by

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Your pattern requires one character of each type, in order. If you want to match all the characters, put them in a single character class, and quantify it with *

pattern="[a-ZA-Z0-9._]*"

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solved Check if input field can only consist of lower and uppercase letters, numbers and the characters . and _