While loop

The Syntax of the While loop is as shown below

                            
while (condition) {
 
  // (While body)
  // statements to execute as long as the condition is true 
  
}
  
                        
                            
                        

While loop executes its body only if the condition is true.

How it works

1. The loop evaluates its condition.
2. If the condition is true then the While body executes. If the condition is false loop ends.
3. Goto to step 2

While Loop Example

                            
let i = 0;
while (i < 5) {
  console.log(i);
  i++;
}
 
** Console ***
 

 
 
                            
                        
                            
                        

Do While Loop

The syntax of do While loop is as shown below.

In the following example, we remove all the break statements. Here the execution starts from the - operator but does not end in that case clause. The execution continues to * ,/ & even to the default clause.

                            

do {
 
 // (While body)
 // statements to execute as long as the condition is true 


} while (condition);
 
                            
                        
                            
                        

The do while loop tests its condition after it executes the while body. Hence the while body executes at least once.

How it works

1. The loop body executes
2. loop evaluates its condition.
3. If the condition is true the loop body executes. If the condition is false loop ends
4. Goto to step 2

Do While Loop Example

                            
let k = 100;
do {
  console.log(k);
  k++;
} while (k < 105);
 
*** Console ***
100
101
102
103
104
 
 
                            
                        
                            
                        

Use Break to break out of the loop

We can use the break statement to break out of a loop

                            
 let j = 200;
 
 do {
  
   console.log(j);
   j++;
  
   if (j > 205) break;
  
  
 } while (true);
  
 **Console **
 200
 201
 202
 203
 204
 205
 
 
                            
                        
                            
                        

Reference

do… while

Read More

1. JavaScript Tutorial
2. If, else if & nested if statements
3. Switch Statement
4. For Loop in JavaScript
5. Break Statement
6. Continue Statement