Why push data to array on async/await?

[jiho5993]

in func.js

const p = (res) => {
    return new Promise((resolve, reject) => {
        res.push('2');
        resolve(res);
    });
};

in main.js

const run = async () => {
    const res = [];
    res.push('1');
    
    console.log('before...');
    for (const item of res) console.log(item);
    
    try {
        await p(res); // call p func in func.js
        
        console.log('after...');
        for (const item of res) console.log(item); // ???
    } catch (e) {
        console.log('ERROR');
    }
};

run();
/** result
 * before...
 * 1
 * after...
 * 1
 * 2
 */

func.js declare promise function and main.js run promise function using async/await.

Why push 2 to res array if i don't assign returned new array?
Does the resolve function have the same property as the pointer of the C language?

[palamarchukser]

it happens because you are passing the link to an array. to avoid this behaviour
await p([...res]); // call p func in func.js

before...
1
after...
1

[jiho5993]

thank you!
So, Is the execution result of the code I uploaded like that?
or I want to know keyword related to this.

[palamarchukser]

didn't really understand the question
just change, from await p(res); to await p([...res]);

[himself65]

Because an array in js is a reference to an object(like a pointer in C), in your code, you passed into a reference and push a number 2. So that's how it works.

[...x] is the spread syntax, which returns items from x, then creates a new array from the items
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Spread_syntax