JSFiddle - React, Tailwind, and code Playground

HTML

Number: <input type="text" onchange="ValidateNumericValue(this);" /><br />
Something else: <input type="text" />

JavaScript

function ValidateNumericValue(oInput) {
    var blnRequired = true; //set to false if allowing empty value
    
    var sValue = oInput.value;
    if (blnRequired && sValue.length == 0) {
        alert("Please enter a value");
        oInput.focus();
        return;
    }
    
    var numericValue = parseFloat(sValue);
    if (isNaN(numericValue)) {
        alert("Value is not a valid number");
        oInput.focus();
        return;
    }
    
    //put back to make 2.15A back to 2.15
    oInput.value = numericValue + "";
}