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<input type='text' inputmode='numeric' pattern='[0-9]+'>
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function validateInut (el) {
  el.addEventListener("beforeinput", function (e) {
    let beforeValue = el.value;
    e.target.addEventListener(
      "input",
      function () {
        if (el.validity.patternMismatch) {
          el.value = beforeValue;
        }
      },
      { once: true }
    );
  })
}

ONLINE DEMO

拓展: MDN - ValidityState