数据处理

• 多字段（数字类型）排序

let arr = [             {name: 'jim', math: 85, english: 66, chinese: 36},             {name: 'tom', math: 78, english: 70, chinese: 87},             {name: 'lilei', math: 78, english: 89, chinese: 36},             {name: 'alice', math: 90, english: 20, chinese: 60},             {name: 'hanmei', math: 54, english: 90, chinese: 96},         ]         arr.sort((a, b) => {             if(a.math !== b.math){             	// a-b就是升序，先按照数学升序排                 return a.math - b.math             } else if(a.english !== b.english) {             	// b-a就是降序，再按照英语降序排                 return b.english - a.english             }ele if(){ 				// 再按照语文降序排 				return b.chinese - a.chinese 			}         })