监听input的输入数字

/**
 * 监听input的数据数字
 * @param count 限制数量
 * @param contentId input/textarea 输入框的id
 * @param limitId 展示数字的span
 */
function initLimit(count, contentId, limitId) {
    var lim = new limit();
    lim.txtNote = document.getElementById(contentId);
    lim.txtLimit = document.getElementById(limitId);
    lim.limitCount = count;
    lim.init();

    function limit() {
        var txtNote;//文本框
        var txtLimit;//提示字数的input
        var limitCount;//限制的字数
        var txtLength;//到达限制时，字符串的长度
        this.init = function () {
            txtNote = this.txtNote;
            txtLimit = this.txtLimit;
            limitCount = this.limitCount;
            txtNote.oninput = function () {
                wordsLimit()
            };
            txtNote.oninput = function () {
                wordsLimit()
            };
            txtLimit.innerText = limitCount;
        };

        function wordsLimit() {
            var noteCount = txtNote.value.length;
            var InPut = document.getElementById(contentId).value.length;
            if (InPut < 1) {
                //document.getElementById("stay").style.display="none";
            }
            if (InPut >= 1) {
                //document.getElementById("stay").style.display="inline";
                //document.getElementById("stay").style.color="green";
            }
            if (InPut > 70) {
                //document.getElementById("stay").style.color="red";
            }
            if (noteCount > limitCount) {
                txtNote.value = txtNote.value.substring(0, limitCount);
                txtLimit.innerText = 0;
            } else {
                txtLimit.innerText = limitCount - noteCount;
            }
            txtLength = txtNote.value.length;//记录每次输入后的长度
        }
    }
}