Test Your JavaScript Skills : ES10 (JavaScript 2019) - 45

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.reject(1);    
      }
   
      let genobj = fx();
      genobj.next().then(v => console.log("Success",v), v => console.log("Reject",v));
   

   a.Reject 1

   b.undefined

   c.error

   d.true

   e.Success 1

   Answer: a

   Reason: The rejected value is 1.

2. Identify the output of the below program

    let obj = {
        name:"ram",
        age:30,
        salary:1000
    };
   
    let {name, ...rest} = obj;
    console.log (name);
   

   a.undefined

   b.name

   c.ram

   d.error

   e.null

   Answer:c

   Reason:The value name variable has is ram.

3. Identify the output of the below program

    let obj = {
        age:30,
        salary:1000
    };
   
    let {age, ...rest} = obj;
    console.log(rest);
   

   a.{age:30}

   b.{salary:1000}

   c.error

   d.undefined

   e.salary

   Answer:b

   Reason:The variable rest has value is {salary:3000}.

4. Identify the output of the below program

    let obj = {
        age:30,
        salary:1000
    };
   
    let {...rest, age} = obj;
    console.log(rest);
   

   a.{age:30}

   b.{salary:1000}

   c.undefined

   d.error

   e.null

   Answer:d

   Reason:The syntax is invalid.

5. Identify the output of the below program

    let obj = {
        name:"ram",    
    };
   
    let obj2 = {
        name2:"gopi",    
    };
   
    let obj4 = {...obj, ...obj2}; 
    console.log(obj4);
   

   a.{name:'ram', name2:'gopi'}

   b.error

   c.undefined

   d.{name:'ram'}

   e.{name2:'gopi'}

   Answer:a

   Reason: Both the objects are merged into obj4.

6. Identify the output of the below program

   
    let prm = new Promise((resolve, reject) => {
        setTimeout(() => {        
            reject("Rejected");
        }, 1000);
    });
   
    prm.then(
            (data) => {
                console.log(data);
            },
            (error) => { }
        ).finally(() => {
            console.log("Finally");
        });
   

   a.Rejected

   b.Error

   c.Finally

   d.undefined

   e.null

   Answer:c

   Reason:The finally block is executed.

7. Identify the output of the below program

    let obj = {
        name:"ram",    
    };
   
    let obj3 = {...obj}; 
    console.log(obj3);
   

   a.{name:'ram'}

   b.ram

   c.undefined

   d.error

   e.null

   Answer:a

   Reason:The spread operator creates a shallow copy of obj.

8. Identify the output of the below program

    let prm = new Promise((resolve, reject) => {
        setTimeout(() => {        
            resolve("Resolve");
        }, 1000);
    });
   
    prm.then(
            (data) => {            
            },
            (error) => { }
        ).finally(() => {
            console.log("Finally");
    });
   

   a.Resolve

   b.Finally

   c.Error

   d.undefined

   e.null

   Answer:b

   Reason:The finally() function when executed it prints finally.

9. Identify the output of the below program

    let obj = {
        name:"ram",
        age:30,
        salary:1000
    };
   
    let obj3 = {...obj}; 
    if (obj3 == obj)
      console.log("same");
    else
      console.log("different");
   

   a.same

   b.different

   c.no output

   d.undefined

   e.error

   Answer: b

   Reason: Both objects are not same i.e located at different locations in memory.

10. Identify the output of the below program

    let obj = {
        age:30,
        salary:1000
    };
    
    let {...rest, ...rest2} = obj;
    console.log(rest);
    

    a.{age:30}

    b.{salary:1000}

    c.undefined

    d.null

    e.error

    Answer:e

    Reason:The rest syntax is invalid.