输入框输入字数限制

 <input class="name" id="name" type="text" placeholder="请输入" onkeyup="checkLength(this, 8);" />

var checkLength = function(dom, maxLength){
    var l = 0;
    for(var i=0; i<dom.value.length; i++) {
        if (/[\u4e00-\u9fa5]/.test(dom.value[i])) {
            l+=2;
        } else {
            l++;
        }
        if (l > maxLength) {
            dom.value = dom.value.substr(0,i);
            alert('字数超出范围![1,4]');
            break;
        }
    }
};