JavaScriptめも

sample.js

//関数宣言
function add(x, y) {
  return x + y;
};
console.log(add(1, 2));  // => 3

//即時関数
(function (x, y) {
    console.log(x + y);
}(1, 2)); // => 3

//関数代入
var test = function (x, y) {
    return x + y;
};
console.log(test(1, 2)); // => 3

//ラムダ
var test = (x, y) => x + y;
console.log(test(1,2)); // => 3

//配列
var array = [1,2,3]
console.log(array[0]) //=> 1

//連想配列
var array2 = {
            a : true,
            b  : false,
            c : false
        };
console.log(array2['a']) //=> true

//Promise then 非同期処理
var sample = new Promise(function(resolve, reject) {
    setTimeout(function() {
        resolve();
    }, 1000);
});
sample.then(function(value) {
    console.log("Promise成功!");
});
console.log("先に出力");

非同期

asyncとawait

sample.js

const test = async () => {
    console.log(1);
    await new Promise((resolve) => {
        setTimeout(() => {
            console.log(2);
            resolve();
        },1000)
    })
}

const main = async () => {
    await test();
    console.log(3);
}

main()

testからasyncとawaitを外す

sample.js

const test = () => {
    console.log(1);
     return new Promise((resolve) => {
        setTimeout(() => {
            console.log(2);
            resolve();
        },1000)
    })
}

const main = async () => {
    await test();
    console.log(3);
}

main()

mainからもasyncとawaitを外す

sample.js

const test = () => {
    console.log(1);
     return new Promise((resolve) => {
        setTimeout(() => {
            console.log(2);
            resolve();
        },1000)
    })
}

const main = async () => {
    await test();
    console.log(3);
}

main()