Promises Output Questions
1. What is the output of this code?
console.log("A");
setTimeout(() => {
console.log("B");
}, 1000);
console.log("C");
setTimeout(() => {
console.log("D");
}, 0);
console.log("E");
Click to see the output
A
C
E
D
B
2. What is the output of this code?
console.log("A");
Promise.resolve().then(() => console.log("B"));
console.log("C");
Click to see the output
A
C
B
3. What is the output of this code?
async function foo() {
console.log("A");
await Promise.resolve();
console.log("B");
}
foo();
console.log("C");
Click to see the output
A
C
B
4. What is the output of this code?
setTimeout(() => console.log("A"), 0);
Promise.resolve().then(() => console.log("B"));
console.log("C");
Click to see the output
C
B
A
5. What is the output of this code?
const promise = new Promise((resolve, reject) => {
console.log("A");
resolve("B");
});
promise.then((res) => console.log(res));
console.log("C");
Click to see the output
A
C
B
6. What is the output of this code?
const promise = new Promise((resolve, reject) => {
console.log("A");
resolve("B");
});
promise.then((res) => console.log(res));
setTimeout(() => console.log("C"), 0);
console.log("D");
Click to see the output
A
D
B
C
7. What is the output of this code?
console.log("A");
setTimeout(() => console.log("B"), 1000);
setTimeout(() => console.log("C"), 0);
console.log("D");
Click to see the output
A
D
C
B
8. What is the output of this code?
async function test() {
console.log("A");
await new Promise((resolve) => setTimeout(resolve, 1000));
console.log("B");
}
test();
console.log("C");
Click to see the output
A
C
B
9. What is the output of this code?
function foo() {
return new Promise((resolve) => {
setTimeout(() => resolve("A"), 1000);
});
}
foo().then((res) => console.log(res));
console.log("B");
Click to see the output
B
A
10. What is the output of this code?
console.log("A");
setTimeout(() => console.log("B"), 0);
Promise.resolve().then(() => console.log("C"));
console.log("D");
Click to see the output
A
D
C
B
11. What is the output of this code?
async function foo() {
console.log("A");
const res = await Promise.resolve("B");
console.log(res);
}
foo();
console.log("C");
Click to see the output
A
C
B
12. What is the output of this code?
setTimeout(() => console.log("A"), 0);
Promise.reject("B").catch((err) => console.log(err));
console.log("C");
Click to see the output
C
B
A
13. What is the output of this code?
async function foo() {
try {
console.log("A");
throw new Error("B");
} catch (err) {
console.log(err.message);
}
console.log("C");
}
foo();
Click to see the output
A
B
C
14. What is the output of this code?
console.log("A");
setTimeout(() => console.log("B"), 0);
Promise.resolve().then(() => {
console.log("C");
setTimeout(() => console.log("D"), 0);
});
console.log("E");
Click to see the output
A
E
C
B
D
15. What is the output of this code?
console.log("A");
setTimeout(() => console.log("B"), 0);
setTimeout(() => console.log("C"), 1000);
console.log("D");
Click to see the output
A
D
B
C
16. What is the output of this code?
Promise.resolve()
.then(() => {
console.log("A");
return Promise.resolve("B");
})
.then((res) => console.log(res));
console.log("C");
Click to see the output
C
A
B
17. What is the output of this code?
async function foo() {
console.log("A");
return "B";
}
foo().then((res) => console.log(res));
console.log("C");
Click to see the output
A
C
B
18. What is the output of this code?
console.log("A");
Promise.resolve().then(() => {
console.log("B");
setTimeout(() => console.log("C"), 0);
});
console.log("D");
Click to see the output
A
D
B
C
19. What is the output of this code?
async function foo() {
console.log("A");
return new Promise((resolve) => setTimeout(() => resolve("B"), 1000));
}
foo().then((res) => console.log(res));
console.log("C");
Click to see the output
A
C
B
20. What is the output of this code?
console.log("A");
Promise.reject("B").catch((err) => console.log(err));
Promise.resolve().then(() => console.log("C"));
console.log("D");
Click to see the output
A
D
B
C
