Do...Loop
Statement
Do [While | Until condition] [statements] [EXIT Do] [statements] Loop
or
Do [statements] [EXIT Do] [statements] Loop [While | Until condition]
Description
Do...Loop repeats a block of statements While a given condition is TRUE, or Until a given condition becomes TRUE. The required component, condition, is any expression that can be evaluated as TRUE or FALSE. The optional component, statements, are the statements executed during the body of the loop. Any number of optional Exit Do statements can be used to exit a loop before it is finished. Do...Loop statements can be nested, and any Exit DO statements in a nested loop transfer execution to one level above the loop where the Exit Do occurs.
Placing the While/Until clause directly after Do causes condition to be evaluated before the first loop is executed, if condition is FALSE statements are never executed; placing the While/Until clause after Loop causes the body of the loop to be executed before condition is evaluated, statements will always be executed, at least once.
Example (Basic)
Rem Do...Loop Example 'Do...Loop repeats a block of statements Dim Counter Counter = 1 'Loop that prints 1 to 5 Do While Counter < 6 Print "Do While...Loop:", Counter Counter = Counter + 1 Loop Print 'Infinite loop that uses Exit Do to terminate Counter = 1000 Do Print "Infinite Loop:", Counter If Counter >= 1000000 Then Exit Do Counter = Counter * 10 Loop
Example (JavaScript)
// Do...Loop Example
/* Do...Loop repeats a block of statements */
var Counter;
Counter = 1;
//Loop that prints 1 to 5
while (Counter < 6) {
document.write("Do While...Loop: " + Counter + "<br>");
Counter = Counter + 1;
}
document.write("<br>");
//Infinite loop that uses Break to terminate
Counter = 1000;
do {
document.write("Infinite Loop: " + Counter + "<br>");
if(Counter >= 1000000 ) { break; }
Counter = Counter * 10;
} while(0<1);
Output
Do While...Loop: 1 Do While...Loop: 2 Do While...Loop: 3 Do While...Loop: 4 Do While...Loop: 5 Infinite Loop: 1000 Infinite Loop: 10000 Infinite Loop: 100000 Infinite Loop: 1000000