JavaScript : break & continue Keywords

What is break keyword?

The break keyword is used for

Exiting from a loop
Exiting from a loop to a label
Exiting from a block to a label

Using break keyword

Case 1 : Inside a loop


  let i=10;
  while (true) {
      i++;
      if (i>15)
       break;
  }

  console.log("i", i); // 16

In the above code the the while is exited when i is 16.

Case 2: Exiting from a loop to a label

  outer: for (let i=0;i<10;i++) {  // outer label
      console.log("for i", i); // for i 0
      for (let j=2;j<10;j++) {
          if (j==5) 
              break outer;
      }    
  }
  console.log("after for loop");

In the above code the inner for loop is exited to outer label.

Case 3: Exiting from a code block to a label


  flagpost: {  // flagpost label
      console.log("inside block");
      break flagpost;
      console.log("inside block 2");  // not executed 
   }
   console.log("after code block");

In the above code the code block is exited to label flagpost.

What is continue keyword?

The continue keyword is used for

To skip instructions in loop and return the control back to start of loop

Using continue Keyword

Case 1

  let i=2;
  while(i<10) { 
    i++;
    if (i> 6)
       console.log(i);
    else
       continue;   
    console.log("After if");
  }

In the above code 'After if' is printed when i is greater than 6. When i less than 7 control is returned back to start of loop.

Case 2
```
  let i=2;
  while(i<10) {
      (i < 6) ? console.log(i): continue; 
      i++;
  }
```
The above code will yield into error because continue keyword cannot be used with ternary operator.

Complete Code Listing

//Objective : Using break and continue keywords
//Author : Mahavir
let i=10;
while (true) {
    i++;
    if (i>15)
     break;
}

console.log("i", i); // 16

outer: for (let i=0;i<10;i++) {  // outer label
    console.log("for i", i); // for i 0
    for (let j=2;j<10;j++) {
        if (j==5) 
            break outer;
    }    
}
console.log("after for loop");


flagpost: {  // flagpost label
    console.log("inside block");
    break flagpost;
    console.log("inside block 2");  // not executed 
 }
 console.log("after code block");


i=2;
while(i<10) { 
  i++;
  if (i> 6)
     console.log(i);
  else
     continue;   
  console.log("After if");
}

i=2;
while(i<10) {
    (i < 6) ? console.log(i): continue;  // error
    i++;
}