<input id="id1" type="number" min="100">

<button onclick="myFunction()">OK</button>

<p id="demo"></p>

<script>

function myFunction() {

    var txt = "";

    if (document.getElementById("id1").validity.rangeUnderflow) {

       txt = "输入的值太小了";

    }

    document.getElementById("demo").innerHTML = txt;

}

</script>

​