html

    clear

 

js

//去空白    function clearFun(str) {        str = str.replace(/^\s+/, '');        for (var i = str.length - 1; i >= 0; i--) {            if (/\S/.test(str.charAt(i))) {                   str = str.substring(0, i + 1);                break;            }        }        return str;    }    document.getElementsByTagName('button')[0].onclick = function() {        var text = document.getElementById('text').value;         var clearText = clearFun(text);        document.getElementById('text').value = clearText;    }

可以去除空格，看不见的字符什么的