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## Repeat until the input is correct

importance: 5

Write a loop which prompts for a number greater than `100`. If the visitor enters another number – ask them to input again.

The loop must ask for a number until either the visitor enters a number greater than `100` or cancels the input/enters an empty line.

Here we can assume that the visitor only inputs numbers. There’s no need to implement a special handling for a non-numeric input in this task.

Run the demo

``````let num;

do {
num = prompt("Enter a number greater than 100?", 0);
} while (num <= 100 && num);``````

The loop `do..while` repeats while both checks are truthy:

1. The check for `num <= 100` – that is, the entered value is still not greater than `100`.
2. The check `&& num` is false when `num` is `null` or an empty string. Then the `while` loop stops too.

P.S. If `num` is `null` then `num <= 100` is `true`, so without the 2nd check the loop wouldn’t stop if the user clicks CANCEL. Both checks are required.