JavaScript

The while loop repeats a block of code as long as a condition is true.
It’s useful when you don’t know how many times the loop should run.

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✅ Syntax

while (condition) {
  // code to run
}

• The loop will continue while the condition is true.
• Make sure to update the condition inside the loop, or it may run forever!

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🔢 Example: Count from 1 to 5

let i = 1;

while (i <= 5) {
  console.log(i);
  i++;
}

Output:

1
2
3
4
5

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⚠️ Infinite Loop Warning

If you forget to update the variable, the condition may never become false:

let i = 1;

while (i <= 5) {
  console.log(i);
  // i++ is missing! This is an infinite loop
}

➡️ Always ensure the loop will eventually exit.

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🔄 Looping Over Arrays

You can also use a while loop to go through an array:

let colors = ["red", "green", "blue"];
let index = 0;

while (index < colors.length) {
  console.log(colors[index]);
  index++;
}

Output:

red
green
blue

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🔁 while vs for loop

• Use for when you know the number of iterations.
• Use while when you want to loop until a certain condition is met (and don’t know how many times).

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✅ Do You Need the Loop to Run at Least Once?

Use a do...while loop instead!

let i = 1;

do {
  console.log(i);
  i++;
} while (i <= 5);

🔹 do...while runs the block at least once, even if the condition is false the first time.

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🧾 Summary

Feature	while Loop
Condition check	Before loop starts
Runs at least once?	❌ No (use do...while)
Best use case	Unknown number of loops

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