JSFiddle - React, Tailwind, and code Playground

HTML

<form id="myform">
    <input name="myInput" 
           required="required" 
           placeholder="Must contain Mickey" 
           pattern=".*Mickey.*" 
           title="must contain Mickey somewhere."
    />
    <input type="submit" />
</form>

JavaScript

/* javascript fallback for old browsers */
//get a collection of all required fields
var requiredFields = document.querySelectorAll("#myform [required]");
//test for native validation
if (typeof requiredFields[0].willValidate !== "undefined") { 
    // native validation available 
} else {
    // native validation not available 
    // so implement our own:
    document.getElementById("myform").onsubmit = function(){      
        for (i = 0; i < requiredFields.length; ++i) {
            var thisField = requiredFields[i];
            var re = new RegExp(thisField.pattern, "i");
            if(!re.exec(thisField.value)){
                //tell the user
                alert(thisField.name+" "+thisField.title);
                //prevent submission
                return false;
            }
        }
    }
}