![[Web front-end] Node.js quick start](https://img.php.cn/upload/course/000/000/067/662b5d34ba7c0227.png)
PHPzCorrection status：qualified
Teacher's comments：
Collection
Collection
<!DOCTYPE html><html lang="zh-CN"><head><meta charset="UTF-8"><meta http-equiv="X-UA-Compatible" content="IE=edge"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>js数据类型、分支、循环</title></head><body><script>// 数据类型let a='OK';console.log(typeof a);console.log('--------------------------');let b=100;console.log(typeof b);console.log('--------------------------');let c=['姓名','年龄','学历'];console.log(typeof c);console.log('--------------------------');let d;console.log(d);// 分支let age = 60;if(age >=60){console.log('老年人');}console.log('-------------------------');let ages = 35;if(ages >=50){console.log('中年人');}else{console.log('青年人');}console.log('-------------------------');let fs=75;if(fs >=90 && fs<120){console.log('你的分数为：A+');}else if(fs >70 && fs<80){console.log('你的分数为：A');}else if(fs >60 && fs<70){console.log('你的分数为：B+');}else{console.log('你的分数为：B');}const colors =['red','green','blue'];console.log(colors);console.log('-------------------------------------------');// for循环方式for(let i=0; i<colors.length; i++){console.log(colors[i]);}console.log('-------------------------------------------');// for-in循环方式for(let item in colors){console.log(item+':'+colors[item]);}console.log('-------------------------------------------');// for-of 循环方式for(let item of colors.values()){console.log('颜色:'+ item);}console.log('-------------------------------------------');for(let item of colors.keys()){console.log('键值：'+ item);}console.log('-------------------------------------------');for(let item of colors.entries()){console.log('键值+颜色：' + item);}</script></body></html>