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handler.set()

Baseline Widely available

This feature is well established and works across many devices and browser versions. Itโ€™s been available across browsers since โจ2016๋…„ 9์›”โฉ.

handler.set() ๋ฉ”์„œ๋“œ๋Š” ์†์„ฑ ๊ฐ’์„ ์„ค์ •์„ ์œ„ํ•œ ํŠธ๋žฉ์ž…๋‹ˆ๋‹ค.

์‹œ๋„ํ•ด ๋ณด๊ธฐ

const monster1 = { eyeCount: 4 };

const handler1 = {
  set(obj, prop, value) {
    if (prop === "eyeCount" && value % 2 !== 0) {
      console.log("Monsters must have an even number of eyes");
    } else {
      return Reflect.set(...arguments);
    }
  },
};

const proxy1 = new Proxy(monster1, handler1);

proxy1.eyeCount = 1;
// Expected output: "Monsters must have an even number of eyes"

console.log(proxy1.eyeCount);
// Expected output: 4

proxy1.eyeCount = 2;
console.log(proxy1.eyeCount);
// Expected output: 2

๊ตฌ๋ฌธ

js
new Proxy(target, {
  set(target, property, value, receiver) {},
});

๋งค๊ฐœ ๋ณ€์ˆ˜

๋‹ค์Œ ๋งค๊ฐœ๋ณ€์ˆ˜๋Š” set() ๋ฉ”์„œ๋“œ์— ์ „๋‹ฌ๋ฉ๋‹ˆ๋‹ค. this๋Š” ์ฒ˜๋ฆฌ๊ธฐ์— ๋ฐ”์ธ๋”ฉ๋ฉ๋‹ˆ๋‹ค.

target

๋Œ€์ƒ ๊ฐ์ฒด

property

์„ค์ •ํ•  ์†์„ฑ์˜ ์ด๋ฆ„ ๋˜๋Š” Symbol

value

์„ค์ •ํ•  ์†์„ฑ์˜ ์ƒˆ ๊ฐ’

receiver

ํ• ๋‹น์ด ์ง€์‹œ๋œ ์›๋ž˜ ๊ฐ์ฒด์ž…๋‹ˆ๋‹ค. ์ด๊ฒƒ์€ ์ผ๋ฐ˜์ ์œผ๋กœ ํ”„๋ก์‹œ ์ž์ฒด์ž…๋‹ˆ๋‹ค. ๊ทธ๋Ÿฌ๋‚˜ set() ์ฒ˜๋ฆฌ๊ธฐ๋Š” ํ”„๋กœํ† ํƒ€์ž… ์ฒด์ธ์ด๋‚˜ ๋‹ค์–‘ํ•œ ๋‹ค๋ฅธ ๋ฐฉ๋ฒ• ๋“ฑ์„ ํ†ตํ•ด ๊ฐ„์ ‘์ ์œผ๋กœ ํ˜ธ์ถœํ•  ์ˆ˜๋„ ์žˆ์Šต๋‹ˆ๋‹ค.

์˜ˆ๋ฅผ ๋“ค์–ด, ์Šคํฌ๋ฆฝํŠธ๊ฐ€ obj.name = "jen"์„ ์ˆ˜ํ–‰ํ•˜๋Š”๋ฐ, obj๋Š” ํ”„๋ก์‹œ๊ฐ€ ์•„๋‹ˆ๋ฉด์„œ ์†์„ฑ .name์ด ์—†๊ณ , ํ”„๋กœํ† ํƒ€์ž… ์ฒด์ธ์—๋Š” ํ”„๋ก์‹œ๊ฐ€ ์žˆ๋‹ค๊ณ  ๊ฐ€์ •ํ•ด๋ด…์‹œ๋‹ค. ์ด๋–„ ํ•ด๋‹น ํ”„๋ก์‹œ์˜ set() ์ฒ˜๋ฆฌ๊ธฐ๊ฐ€ ํ˜ธ์ถœ๋˜๊ณ ๋‚˜์„œ obj๊ฐ€ ์ˆ˜์‹ ์ž๋กœ ์ „๋‹ฌ๋ฉ๋‹ˆ๋‹ค.

๋ฐ˜ํ™˜ ๊ฐ’

set() ๋ฉ”์„œ๋“œ๋Š” ๋ถˆ๋ฆฌ์–ธ ๊ฐ’์„ ๋ฐ˜ํ™˜ํ•ฉ๋‹ˆ๋‹ค.

  • ํ• ๋‹น์ด ์„ฑ๊ณตํ–ˆ์œผ๋ฉด true๋ฅผ ๋ฐ˜ํ™˜ํ•ฉ๋‹ˆ๋‹ค.
  • ์—„๊ฒฉ ๋ชจ๋“œ์—์„œ set() ๋ฉ”์„œ๋“œ๊ฐ€ false๋ฅผ ๋ฐ˜ํ™˜ํ•˜๋ฉด TypeError ์˜ˆ์™ธ๊ฐ€ ๋ฐœ์ƒํ•ฉ๋‹ˆ๋‹ค.

์„ค๋ช…

handler.set() ๋ฉ”์„œ๋“œ๋Š” ์†์„ฑ ๊ฐ’์„ ์„ค์ •์„ ์œ„ํ•œ ํŠธ๋žฉ์ž…๋‹ˆ๋‹ค.

๊ฐ€๋กœ์ฑ„๊ธฐ

์ด ํŠธ๋žฉ์€ ๋‹ค์Œ ์ž‘์—…์„ ๊ฐ€๋กœ์ฑŒ ์ˆ˜ ์žˆ์Šต๋‹ˆ๋‹ค.

  • ์†์„ฑ ํ• ๋‹น: proxy[foo] = bar์™€ proxy.foo = bar
  • ์ƒ์†๋œ ์†์„ฑ ํ• ๋‹น: Object.create(proxy)[foo] = bar
  • Reflect.set()

๋ถˆ๋ณ€ ์กฐ๊ฑด

๋‹ค์Œ ๋ถˆ๋ณ€ ์กฐ๊ฑด์ด ์œ„๋ฐ˜๋˜๋ฉด ํ”„๋ก์‹œ์—์„œ TypeError๊ฐ€ ๋ฐœ์ƒํ•ฉ๋‹ˆ๋‹ค.

  • ๋Œ€์ƒ ๊ฐ์ฒด ์†์„ฑ์ด ์“ฐ๊ธฐ ๋ฐ ๊ตฌ์„ฑํ•  ์ˆ˜ ์—†๋Š” ๋ฐ์ดํ„ฐ ์†์„ฑ์ธ ๊ฒฝ์šฐ, ์†์„ฑ ๊ฐ’์„ ๋Œ€์ƒ ๊ฐ์ฒด ์†์„ฑ์˜ ๊ฐ’๊ณผ ๋‹ค๋ฅด๊ฒŒ ๋ณ€๊ฒฝํ•  ์ˆ˜ ์—†์Šต๋‹ˆ๋‹ค.
  • ๋Œ€์ƒ ๊ฐ์ฒด ์†์„ฑ์˜ [[Set]] ์†์„ฑ์ด undefined ์ธ ๊ตฌ์„ฑ ๋ถˆ๊ฐ€๋Šฅํ•œ ์ ‘๊ทผ์ž ์†์„ฑ์ธ ๊ฒฝ์šฐ, ์†์„ฑ ๊ฐ’์„ ์„ค์ •ํ•  ์ˆ˜ ์—†์Šต๋‹ˆ๋‹ค.
  • ์—„๊ฒฉ ๋ชจ๋“œ์—์„œ set() ์ฒ˜๋ฆฌ๊ธฐ๊ฐ€ false๋ฅผ ๋ฐ˜ํ™˜ํ•˜๋ฉด TypeError ์˜ˆ์™ธ๊ฐ€ ๋ฐœ์ƒํ•ฉ๋‹ˆ๋‹ค.

์˜ˆ์ œ

์†์„ฑ ๊ฐ’ ์„ค์ • ํŠธ๋žฉ

๋‹ค์Œ ์ฝ”๋“œ๋Š” ์†์„ฑ ๊ฐ’์„ ์„ค์ •ํ•˜๋Š” ๊ฒƒ์„ ํŠธ๋žฉํ•ฉ๋‹ˆ๋‹ค.

js
const p = new Proxy(
  {},
  {
    set(target, prop, value, receiver) {
      target[prop] = value;
      console.log(`property set: ${prop} = ${value}`);
      return true;
    },
  },
);

console.log("a" in p); // false

p.a = 10; // "property set: a = 10"
console.log("a" in p); // true
console.log(p.a); // 10

๋ช…์„ธ์„œ

Specification
ECMAScriptยฎ 2026 Language Specification
# sec-proxy-object-internal-methods-and-internal-slots-set-p-v-receiver

๋ธŒ๋ผ์šฐ์ € ํ˜ธํ™˜์„ฑ

๊ฐ™์ด ๋ณด๊ธฐ