Test Your JavaScript Skills : ES9 (JavaScript 2018) - 44

Introduction

Namaste, In this blog I will discuss 10 code scenarios on Javascript .

1. Identify the output of the below program

    async function* fx() {
        yield await Promise.resolve(1);
        yield await Promise.resolve(2);
        yield await Promise.resolve(3);
      }
   
      let genobj = fx();
      genobj.next().then(v => console.log(v.value));
   

   a.1

   b.2

   c.3

   d.undefined

   e.error

   Answer:a

   Reason:The return value is 1.

2. Identify the output of the below program

   
    async function* fx() {
        yield await Promise.resolve(100);  
      }
   
      let genobj = fx();
      genobj.next().then(v => console.log());
      genobj.next().then(v => console.log(v.done));
   

   a.true

   b.false

   c.100

   d.undefined

   e.error

   Answer:a

   Reason:The return value is true.

3. Identify the output of the below program

    async function* fx() {
        yield await Promise.resolve(10);    
      }
   
      async function forawait() {
          for await (let obj of fx()) {
              console.log(obj);
          }
      }
   
      forawait();
   

   a.10

   b.false

   c.true

   d.undefined

   e.error

   Answer: a

   Reason:The value is 10.

4. Identify the output of the below program

    async function* fx() {
        yield await Promise.resolve(10);    
      }
   
      async function forawait() {
          for await (let obj of fx()) {
              console.log(obj.done);
          }
      }
   
      forawait();
   

   a.true

   b.false

   c.undefined

   d.error

   e.10

   Answer:c

   Reason:The done property does not exist.

5. Identify the output of the below program

    async function* fx() {
        yield await Promise.reject(10);    
      }
   
      async function forawait() {
          for await (let obj of fx()) {
              console.log(obj);
          }
      }
   
      forawait();
   

   a.10

   b.undefined

   c.true

   d.false

   e.error

   Answer:e

   Reason:Because of unhandled rejection an error is raised.

6. Identify the output of the below program

    async function* fx() {
        yield await Promise.reject(10);    
      }
   
      async function forawait() {
        try {
          for await (let obj of fx()) {
              console.log(obj);
          }
        }catch (err) {
            console.log(err);
        }
      }
   
      forawait();
   

   a.error

   b.undefined

   c.10

   d.true

   e.false

   Answer:c

   Reason:The rejected value 10 is captured in the catch block.

7. Identify the output of the below program

   
    async function* fx() {
        yield await Promise.resolve(1);
        yield await Promise.resolve(2);
        yield await Promise.resolve(3);
      }
   
      let genobj = fx();
      genobj.next().then(v => console.log(v.done));
   

   a.1

   b.2

   c.true

   d.false

   e.error

   Answer:d

   Reason:The return value for done is false.

8. Identify the output of the below program

   
    async function* fx() {
        yield await Promise.resolve(100);  
      }
   
      let genobj = fx();
      genobj.next().then(v => console.log());
      genobj.next().then(v => console.log(v.value));
   

   a.100

   b.error

   c.undefined

   d.1

   e.false

   Answer:c

   Reason:The return value is undefined.

9. Identify the output of the below program

    async function* fx() {
        yield await Promise.reject(1);    
      }
   
      let genobj = fx();
      genobj.next().then(v => console.log(v.value));
   

   a.error

   b.undefined

   c.false

   d.true

   e.1

   Answer:a

   Reason:Because of unhandled rejection an error is raised.

10. Identify the output of the below program

    async function* fx() {
        yield await Promise.resolve(10);    
      }
    
      async function forawait() {
          for await (let obj of fx()) {
              console.log(obj.value);
          }
      }
    
      forawait();
    

    a.10

    b.true

    c.false

    d.undefined

    e.error

    Answer:d

    Reason:The value property does not exist.