截取固定长度的文字

function getReal(eles,lengths,chars){
        var eles_text=eles.innerHTML;
        var eles_length=eles_text.length;
        if (eles_length>lengths) {
			eles_length=lengths;
		}
        var eles_last=eles_text.slice(lengths-1,lengths);
        // console.log(eles_last);
        if (eles_last=="，"||eles_last=="。"||eles_last=="！"||eles_last==".") {
        	console.log('yes');
        	eles_length+=1;
        }
		eles_text=eles_text.slice(0,eles_length)+chars;
		return eles.innerHTML=eles_text;
	}
	var p=document.getElementsByTagName('p')[0];
	getReal(p,84,'....');