if 判斷

var age1 = 3; if (age1>5){console.log("da3") }else if (age1>2){console.log("da2") }else {console.log("else") }

while循環

while (age1<20){age1 = age1 + 1console.log(age1) } // do while 最少執行一次 do{age1 = age1 + 1console.log(age1) }while (age1<20)

for循環

idea快捷 fori

for (let i = 0; i < 20; i++) {console.log(i) }

forEach 循環

var arr2 = [1,2,5,4,3] arr2.forEach(function (value, index, array) {console.log(value)console.log(index)console.log(array) }) arr2.forEach(function (value, index) {console.log(value)console.log(index) }) arr2.forEach(function (value) {console.log(value) })

for in

var arr2 = [1,2,5,4,3] for (var num in arr2) {if (arr2.hasOwnProperty(num)){console.log("存在")console.log(num)console.log(arr2[num])} }

for of

var arr2 = [1,2,5,4,3] for (let number of arr2) {console.log(number) }

更詳細內容可參考：
https://wangxiaomu.blog.csdn.net/article/details/78444088
https://blog.csdn.net/w390058785/article/details/80522383
https://blog.csdn.net/fu983531588/article/details/89597521

https://www.bilibili.com/video/BV1JJ41177di?p=9

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