index.js

function intToChinese ( str ) {
    str = str+'';
    var len = str.length-1;
    var idxs = ['','十','百','千','万','十','百','千','亿','十','百','千','万','十','百','千','亿'];
    var num = ['零','壹','贰','叁','肆','伍','陆','柒','捌','玖'];
    return str.replace(/([1-9]|0+)/g,function( $, $1, idx, full) {

        var pos = 0;
        if( $1[0] != '0' ){
            pos = len-idx;
            if( idx == 0 && $1[0] == 1 && idxs[len-idx] == '十'){
                return idxs[len-idx];
            }
            return num[$1[0]] + idxs[len-idx];
        } else {
            var left = len - idx;
            var right = len - idx + $1.length;
            if( Math.floor(right/4) - Math.floor(left/4) > 0 ){
                pos = left - left%4;
            }
            if( pos ){
                return idxs[pos] + num[$1[0]];
            } else if( idx + $1.length >= len ){
                return '';
            }else {
                return num[$1[0]]
            }
        }
    });
}

let money = intToChinese(123);
console.log(money);