分享一下js对象常用的扩展

//js string对象扩展
(function() {
    // 除去两边空白 
    String.prototype.trim = function() {
        return this.replace(/(^\s*)|(\s*$)/g, "");
    };
    //截取字符串了 
    String.prototype.cutStr = function(len) {
        var str = this;
        var str_length = 0;
        var str_len = 0;
        str_cut = new String();
        str_len = str.length;
        for (var i = 0; i < str_len; i++) {
            a = str.charAt(i);
            str_length++;
            if (escape(a).length > 4) {
                //中文字符的长度经编码之后大于4  
                str_length++;
            }
            str_cut = str_cut.concat(a);
            if (str_length >= len) {
                str_cut = str_cut.concat("...");
                return str_cut;
            }
        }
        //如果给定字符串小于指定长度，则返回源字符串；  
        if (str_length < len) {
            return str;
        }
    };
    // 保留中文 
    String.prototype.getCn = function() {
        return this.replace(/[u4e00-u9fa5uf900-ufa2d]/g, "");
    };
    // 保留数字 
    String.prototype.getNum = function() {
        return this.replace(/[^\d]/g, "");
    };
    // 保留字母 
    String.prototype.getEn = function() {
        return this.replace(/[^A-Za-z]/g, "");
    };
    //从右边截取，到终点字符位置
    String.prototype.subIndexStr = function(str) {
        var index = this.indexOf(str);
        return this.substr(0, index);
    };
    // 从左截取指定长度的字串 
    String.prototype.left = function(n) {
        return this.slice(0, n);
    };
    // 从右截取指定长度的字串 
    String.prototype.right = function(n) {
        return this.slice(this.length - n);
    };
    // HTML编码 
    String.prototype.HTMLEncode = function() {
        var re = this;
        var q1 = [/x26/g, /x3C/g, /x3E/g, /x20/g];
        var q2 = ["&", "<", ">", " "];
        for (var i = 0; i < q1.length; i++)
            re = re.replace(q1[i], q2[i]);
        return re;
    };
    //字符串转换为日期格式
    String.prototype.toDate = function() {
        if (isNaN(this) && !isNaN(Date.parse(this))) {　　
            return new Date(this);
        } else {
            console.error(this == null ? "不是日期格式" : this + "不是日期格式")
        }
    };
    //左边补零
    String.prototype.padLeftZero = function(n) {
        return Array(n > this.length ? (n - ('' + this).length + 1) : 0).join(0) + this;
    };
    //右边补零
    String.prototype.padRightZero = function(n) {
        return this + Array(n > this.length ? (n - ('' + this).length + 1) : 0).join(0);
    };
    //转换人民币格式
    String.prototype.toRenminbi = function() {
        var n = this.replace(/,/g, '');;
        var fraction = ['角', '分'];
        var digit = ['零', '壹', '贰', '叁', '肆', '伍', '陆', '柒', '捌', '玖'];
        var unit = [
            ['元', '万', '亿'],
            ['', '拾', '佰', '仟']
        ];
        var head = n < 0 ? '欠' : '';
        n = Math.abs(n);

        var s = '';

        for (var i = 0; i < fraction.length; i++) {
            s += (digit[Math.floor(n * 10 * Math.pow(10, i)) % 10] + fraction[i]).replace(/零./, '');
        }
        s = s || '整';
        n = Math.floor(n);

        for (var i = 0; i < unit[0].length && n > 0; i++) {
            var p = '';
            for (var j = 0; j < unit[1].length && n > 0; j++) {
                p = digit[n % 10] + unit[1][j] + p;
                n = Math.floor(n / 10);
            }
            s = p.replace(/(零.)*零$/, '').replace(/^$/, '零') + unit[0][i] + s;
        }
        return head + s.replace(/(零.)*零元/, '元').replace(/(零.)+/g, '零').replace(/^整$/, '零元整');
    };
    String.prototype.amountFormat = function() {
        var number = this;
        var decimals = 2;
        number = (number + '').replace(/[^0-9+-Ee.]/g, '');
        var n = !isFinite(+number) ? 0 : +number,
            prec = !isFinite(+decimals) ? 0 : Math.abs(decimals),
            sep = (typeof thousands_sep === 'undefined') ? ',' : thousands_sep,
            dec = (typeof dec_point === 'undefined') ? '.' : dec_point,
            s = '',
            toFixedFix = function(n, prec) {
                var k = Math.pow(10, prec);
                return '' + Math.floor(n * k) / k;
            };
        s = (prec ? toFixedFix(n, prec) : '' + Math.floor(n)).split('.');
        var re = /(-?\d+)(\d{3})/;

        while (re.test(s[0])) {
            s[0] = s[0].replace(re, "$1" + sep + "$2");
        }

        if ((s[1] || '').length < prec) {
            s[1] = s[1] || '';
            s[1] += new Array(prec - s[1].length + 1).join('0');
        }
        return s.join(dec);
    };
})();

//js  Date 时间对象扩展
(function() {
    Date.prototype.toString = function(fmt) {
        function padLeftZero(str) {
            return ('00' + str).substr(str.length);
        }
        if (/(y+)/.test(fmt)) {
            fmt = fmt.replace(RegExp.$1, (this.getFullYear() + '').substr(4 - RegExp.$1.length));
        }
        let o = {
            'M+': this.getMonth() + 1,
            'd+': this.getDate(),
            'h+': this.getHours(),
            'm+': this.getMinutes(),
            's+': this.getSeconds()
        };
        for (let k in o) {
            if (new RegExp(`(${k})`).test(fmt)) {
                let str = o[k] + '';
                fmt = fmt.replace(RegExp.$1, (RegExp.$1.length === 1) ? str : padLeftZero(str));
            }
        }

        return fmt;
    }
})();