Js文本溢出自动添加省略号ellipsis

 function ellipsis(val, len, word) {
            if (val && val.length > len) {
                if (word) {
                    var vs = val.substr(0, len - 1)
                    var i = Math.max(vs.lastIndexOf(‘ ‘), vs.lastIndexOf(‘.‘), vs.lastIndexOf(‘!‘), vs.lastIndexOf(‘?‘))
                    if ( i !== -1 && i >= (len-15) ) {
                        return vs.substr(0, i) + ‘...‘
                    }
                }
                return val.substr(0, len) + ‘...‘
            }
            return val
        }

var aa="你是谁？萨达哈撒";
 var bb=ellipsis(aa,5);
 console.log(bb);