一些input用法

//设定选中范围
someInput.setSelectionRange(0, 2);

//只读
<input type="text" value="2" readonly />

//绑定键盘输入事件
someInput.addEventListener('keydown', function (event) {
　　//......
});

//获取光标位置
<input type="text" id="text-element" />
<!-- Or a textarea
<textarea id="text-element"></textarea>
-->
<input type="button" id="trigger" value="Check"/>

<script>
    document.getElementById("trigger").addEventListener("click", function(){
        var myElement = document.getElementById('text-element');
        var startPosition = myElement.selectionStart;
        var endPosition = myElement.selectionEnd;
        
        // Check if you've selected text
        if(startPosition == endPosition){
            alert("The position of the cursor is (" + startPosition + "/" + myElement.value.length + ")");
        }else{
            alert("Selected text from ("+ startPosition +" to "+ endPosition + " of " + myElement.value.length + ")");
        }
    },false);
</script>