While & Do While Loops in JavaScript

While & Do While statements keep executing a block of statements in a loop until a given condition evaluates to false.

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 ***

0
1
2
3
4

Do While Loop

The syntax of do While loop is as shown below.

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