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Repair Windows errors before they cause bigger problemsFix Now →Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →Clear out junk files and repair common Windows errorsFree Scan →A do...while loop in TypeScript runs its body first and checks the condition afterward, so the body always executes at least once. Use it when one pass is mandatory and the condition only decides whether to repeat. The syntax is the same as in JavaScript, as documented in MDN’s do…while reference.
Syntax
do {
// statements to run at least once
} while (condition);The closing semicolon is part of the documented syntax. Automatic semicolon insertion may sometimes supply it, but write it explicitly for clarity.
How execution proceeds
- Enter the body and run its statements.
- Evaluate the condition after the body finishes.
- If the condition is true, run the body again. If it is false, continue with the code after the loop.
Because the check comes after the first pass, an initially false condition does not prevent that first pass.
Example: retry until input is valid
let attempts = 0;
let isValid = false;
do {
attempts += 1;
isValid = checkInput();
} while (!isValid && attempts < 3);checkInput() is always called once. The loop repeats only while the input is invalid and fewer than three attempts have been made. Both isValid and attempts are updated inside the body, so the condition can become false.
#1 Best Overall
Exiting early or skipping ahead
Per MDN, break ends the loop immediately and moves control to the code after it. continue skips the rest of the current pass and goes to the condition check; if the condition is true, another iteration follows.
let value = 0;
do {
value += 1;
if (shouldStop(value)) {
break;
}
if (shouldSkip(value)) {
continue;
}
process(value);
} while (value < 10);Note that continue does not bypass the condition. That is why value += 1 sits at the top: the counter changes even on skipped passes.
Rank #2
- TypeScript implements a superset of syntax for strictly typed development, facilitating deep static analysis and enhanced development environment integration. The compiler translates source into standard script formats, ensuring parity across any runtime.
- TypeScript is ideal for front-end developers, full-stack engineers, and software architects who build large-scale web applications. It serves those looking to improve code excellence, reduce bugs through static checking, and maintain complex projects more.
- Lightweight, Classic fit, Double-needle sleeve and bottom hem
do…while versus while
| Aspect | do…while | while |
|---|---|---|
| Condition checked | After the body | Before the body |
| Minimum body runs | One | Zero |
Choose do...while when the first operation is required, such as reading input before you can judge it. Choose while when zero runs is acceptable. As a rule of thumb (a style preference, not a TypeScript restriction), use for for plain counted loops and for...of to visit items when you don’t need an index.
Quick Recap
Best Value
Common mistakes
- Expecting a false condition to skip the body. It will not; the body runs once regardless.
- Leaving out the semicolon. Write
} while (condition);. - No path to termination. If nothing in the body can make the condition false and there is no
break, the loop runs forever. Confirm that the body updates the state the condition reads, or add a deliberate exit. - Using it where zero iterations should be possible. Use
whileinstead.
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