– number, string, boolean, privateがある
– 定数は最初の値を変更できない、変数は変更できる
– varはプルグラム全体、letは宣言された構文の中のみ
let x:number x = 123 console.log(x) x = "ok" console.log(x)
Type ‘string’ is not assignable to type ‘number’. でエラーになる
– let xはlet x:anyと同じでこれであれば型が異なってもOK
– null, undefined, NaNなどの特殊な値も
### 型変換
let x = 123 console.log(x) let y = "456" x = +y // x = Number(y) console.log(x)
テキストを数値にするには、+かNumber()
### 演算
let price = 12500
let withTax = price * 1.1
let woTax = price / 1.1
console.log("price:" + price)
console.log("税別:" + withTax)
console.log("税込" + woTax)
### 制御構文
const num = 12345
const result = num % 2
if (result == 0){
console.log(num + ":偶数")
} else {
console.log(num + ":奇数")
}
== は等しい、===は型も等しい
const month = 7
if(month <= 0)
console.log("不明")
else if(month < 3)
console.log(month + ":冬")
else if(month < 6)
console.log(month + ":春")
else if(month < 9)
console.log(month + ":夏")
else if(month < 12)
console.log(month + ":秋")
else if(month < 13)
console.log(month + ":冬")
else
console.log("不明")
三項演算子
const num = 12345
const result = num % 2 === 0 ? '偶数' : '奇数'
console.log(num + ' is ' + result)
switch
const month = 7
switch(month) {
case 1: console.log(month + " winter"); break
case 2: console.log(month + " winter"); break
case 3: console.log(month + " spring"); break
case 4: console.log(month + " spring"); break
case 5: console.log(month + " spring"); break
case 6: console.log(month + " summer"); break
case 7: console.log(month + " summer"); break
case 8: console.log(month + " summer"); break
case 10: console.log(month + " fall"); break
case 11: console.log(month + " fall"); break
case 12: console.log(month + " winter"); break
default: console.log("不明")
}
do while
const max = 100
let total = 0
let count = 0
while(count <= max) {
total += count++
}
console.log(max + " sum is " + total)
for
const max = 100
let total = 0
for(let i = 1; i <= max; i++){
total += i
}
console.log("total is " + total)
for(let var in value) と for(let var of value) がある
うむ、ここはどの言語でもだいたい同じ
