<div class="coupon-exchange clearfix">

        <div class="code-input">

            <input type="text" placeholder="请输入兑换码" class="input" id="couponExchangeInput"/>

            <i class="icon-clear" id="couponExchangeClear"></i>

        </div>

        <div class="btn-exchange" id="couponExchangeBtn">兑换</div>

    </div>

function couponExchange() {

　　//中文输入，输入完成后才触发事件

    var flag = true;

    $('#couponExchangeInput').on('compositionstart',function(){

        flag = false;

    });

    $('#couponExchangeInput').on('compositionend',function(){

        flag = true;

    });

    $('#couponExchangeInput').on('input', function(){

        var _this = this;

        setTimeout(function(){

            if(flag){

                var _val = $(_this).val();

                $('#couponExchangeBtn').addClass('active');

                $('#couponExchangeClear').css('display', 'block');

                if(_val == ''){

                    $('#couponExchangeBtn').removeClass('active');

                    $('#couponExchangeClear').hide();

                }

                if(strlen(_val) > 100){

                    var _cutVal = cut_str(_val, 50);

                    $(_this).val(_cutVal);

                }

            }

        },0);

    });

    $('#couponExchangeClear').click(function(){

        $('#couponExchangeBtn').removeClass('active');

        $('#couponExchangeClear').hide();

        $('#couponExchangeInput').val('').focus();

    });

    $('#couponExchangeInput').blur(function(){

        var _val = $(this).val();

        if(strlen(_val) > 100){

           var _cutVal = cut_str(_val, 50);

            $(this).val(_cutVal);

        }

    });

    $('#couponExchangeBtn').click(function(){

        if($(this).hasClass('active')){

            console.log(1);

        }

    });

}

//获取字符串的长度，一个中文占位两个字符长度

function strlen(str) {

    var len = 0;

    for (var i = 0; i < str.length; i++) {

        var c = str.charCodeAt(i);

        if ((c >= 0x0001 && c <= 0x007e) || (0xff60 <= c && c <= 0xff9f)) {

            len++;

        }

        else {

            len += 2;

        }

    }

    return len;

}

//截取字符串的长度，一个中文占位两个字符长度

function cut_str(str, len){

    var char_length = 0;

    for (var i = 0; i < str.length; i++){

        var son_str = str.charAt(i);

        encodeURI(son_str).length > 2 ? char_length += 1 : char_length += 0.5;

        if (char_length >= len){

            var sub_len = char_length == len ? i+1 : i;

            return str.substr(0, sub_len);

            break;

        }

    }

}