JA @js_test
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const arr = [1, 2, 3];
arr[-1] = 10;
console.log(arr.length, arr);
function processTransaction(amount) {
try {
if (typeof amount !== 'number') {
throw new TypeError('Amount must be a number');
}
if (amount <= 0) {
throw new RangeError('Amount must be positive');
}
return 'Transaction processed';
} catch (error) {
if (error instanceof TypeError) {
return { status: 'Type Error', message: error.message };
} else if (error instanceof RangeError) {
return { status: 'Range Error', message: error.message };
}
return { status: 'Unknown Error', message: error.message };
}
}
console.log(processTransaction(-50));function recursiveFibonacci(n) {
return n <= 1 ? n : recursiveFibonacci(n - 1) + recursiveFibonacci(n - 2);
}
const result = recursiveFibonacci(6);
console.log(result);function Shape() {}
function Circle(radius) {
this.radius = radius;
}
Circle.prototype = Object.create(Shape.prototype);
Circle.prototype.constructor = Circle;
const shape = new Shape();
const circle = new Circle(5);
console.log(circle instanceof Circle);
console.log(circle instanceof Shape);
console.log(shape instanceof Circle);
console.log(shape instanceof Shape);const user = { name: 'Alice' };
const ratings = new WeakMap();
ratings.set(user, 5);
const result = [];
result.push(ratings.has(user));
result.push(ratings.get(user));
// Create a reference-free object
let tempUser = { name: 'Bob' };
ratings.set(tempUser, 10);
result.push(ratings.has(tempUser));
// Remove the reference
tempUser = null;
// Try to iterate through WeakMap
result.push(typeof ratings[Symbol.iterator]);
console.log(result);const obj = { a: 1, b: 2, c: 3 };
const result = Object.values(obj).reduce((acc, curr) => acc * curr, 1);
console.log(result);const obj = { a: 1 };
const { b } = obj;
console.log(b);console.log(1);
setTimeout(() => {
console.log(2);
Promise.resolve().then(() => console.log(3));
}, 0);
Promise.resolve()
.then(() => {
console.log(4);
setTimeout(() => console.log(5), 0);
})
.then(() => console.log(6));
console.log(7);
function X() {}
X.prototype.getValue = function() {
return this.value;
};
function Y() {
this.value = 42;
}
Y.prototype = Object.create(X.prototype);
Y.prototype.constructor = Y;
var y = new Y();
console.log(y.getValue());function Animal() {}
function Dog() {}
Dog.prototype = Object.create(Animal.prototype);
const rover = new Dog();
console.log(rover.constructor == Animal);const weakSet = new WeakSet();
let obj1 = { id: 1 };
let obj2 = { id: 2 };
let obj3 = obj1;
weakSet.add(obj1);
weakSet.add(obj2);
const results = [
weakSet.has(obj1),
weakSet.has(obj3),
weakSet.has({ id: 2 }),
weakSet.has(obj2)
];
obj1 = null;
console.log(results);
const user = {
name: "Alice",
age: 32,
role: "developer"
};
const handler = {
get(target, prop) {
return prop in target ?
`Value: ${target[prop]}` :
"Not found";
}
};
const proxy = new Proxy(user, handler);
delete user.age;
console.log(Reflect.get(proxy, "name") + ", " + proxy.age + ", " + proxy.skills);async function asyncSumOfSquares() {
const numbers = [2, 3, 4, 100];
const result = await numbers.reduce(async (acc, num) => {
const currentSquare = await Promise.resolve(num * num);
return (await acc) + currentSquare;
}, Promise.resolve(0));
console.log(result);
}
asyncSumOfSquares();
const team = {
name: 'Eagles',
players: ['Smith', 'Johnson', 'Williams'],
coach: { name: 'Brown', experience: 12 },
stats: { wins: 10, losses: 6 }
};
const {
name: teamName,
players: [firstPlayer, , thirdPlayer],
coach: { name },
stats: { wins, draws = 0 }
} = team;
console.log(`${teamName}-${firstPlayer}-${thirdPlayer}-${name}-${wins}-${draws}`);❓Что будет на выходе?
function foo() {
return typeof arguments;
};
console.log(foo(1, 2, 3));const a = 9007199254740991n; // MAX_SAFE_INTEGER as BigInt
const b = 2n;
const c = a + b;
const result = [
a === 9007199254740991,
a + 1n === 9007199254740992n,
typeof c,
c > Number.MAX_SAFE_INTEGER,
BigInt(9007199254740992) - BigInt(9007199254740991)
];
console.log(result);
const weakMap = new WeakMap();
const arr = [{}, {}, {}, []];
arr.forEach((obj, index) => weakMap.set(obj, index));
arr.splice(1, 1);
const result = arr.map(obj => weakMap.get(obj));
console.log(result);
const str = "hello world";
const [a, b, c, d, e, f] = str;
console.log([...[a, b, c, d, e, f], ...str]);
const calculator = {
value: 10,
add: function(x) {
return this.value + x;
},
multiply: function(x) {
return this.value * x;
}
};
const add5 = calculator.add;
const double = calculator.multiply.bind(calculator);
const triple = calculator.multiply.bind({value: 3});
console.log(add5(2) + double(3) + triple(4));