循环：For 循环、While 循环、ForOf 循环、ForIn 循环

for (let i = 1; i <p>要循环数组，我们可以执行以下操作：<br></p><pre class="brush:php;toolbar:false">const animals = ['lizard', 'fish', 'turtle'];for (let i = 0; i <p>我们还可以反向循环这个数组：<br></p><pre class="brush:php;toolbar:false">for (let i = animals.length - 1; i &gt;= 0; i--) {  console.log(i, animals[i]);}// 2 'turtle'// 1 'fish'// 0 'lizard'

for (let i = 0; i <p>如果我们想要迭代数组的数组，这很有用：<br></p><pre class="brush:php;toolbar:false">const seatingchart = [  ['abigale', 'tim', 'cynthia'],  ['bob', 'carter', 'zane', 'tanja'],  ['quin', 'xavier'],];// to print each name individually from seatingchart:for (let i = 0; i <h2>      while 循环</h2><p>简单 while 循环的一个例子是：<br></p><pre class="brush:php;toolbar:false">let num = 0;// to print out 0 through 4:while (num <h2>      中断关键字</h2><p>break关键字可用于退出while循环：<br></p><pre class="brush:php;toolbar:false">let input = prompt('say something:');while (true) {  input = prompt(input);  if (input === 'stop copying me') {    break; // finally stops prompting user  }}

let line = ['abby', 'salvia', 'jamie', 'carter', 'john'];

for (let i = 0; i <h2>      for...of 循环</h2><p>如果我们想打印数组中的每个值，我们可以这样做：<br></p><pre class="brush:php;toolbar:false">let people = ['agitha', 'bruce', 'charlie', 'dane', 'ernie'];// to print each persons name:for (let person of people) {  console.log(person);}

const seatingchart = [  ['abigale', 'tim', 'cynthia'],  ['bob', 'carter', 'zane', 'tanja'],  ['quin', 'xavier'],];// to print each name individually from seatingchart:for (let row of seatingchart) {  for (let person of row) {    console.log(person);  }}

const testscores = {  jim: 34,  abby: 93,  greg: 84,  mark: 95,  melvin: 73,};for (let person in testscores) {  console.log(`${person} scored ${testscores[person]}`);}

let total = 0;let scores = Object.values(testScores);for (let score of scores) {  total += score;}let avg = total / scores.length;console.log(avg);