JS.10.5 Iteration Statements
A 'for' loop consists of three optional expressions, enclosed in parentheses and separated by semi-colons.
for([init-expression];[condition];[increment-expression]) {
statements;
}
The initial-expression is evaluated before the loop starts. It is normally used to declare and initialize a counter variable. The condition statement is evaluated at the beginning of every loop. If the condition is true, the statements are executed. Otherwise, the loop terminates. The increment-expression is executed after the body statements. It is normally used to increment the counter variable.
for(var idx = 0; idx < array1.length; idx++) {
...
}
A special 'for' loop allows iteration through all properties of an object. If the object is an array, each item in the array is treated as a property.
var props = "";
for(var item in obj) {
props += item + " = " + obj[item];
}
A 'while' statement is a loop with a single condition. The condition is evaluated at the beginning of every loop. If the condition is true, the body of the loop is executed. Otherwise, the loop is terminated.
while(condition) {
statements;
}
A slight variation of the 'while' statement is 'do...while'. Instead of evaluating the condition at the beginning of the loop, 'do...while' statement evaluates the condition at the end of a loop. This guarantees the loop is at least executed once.
do {
statements
} while(condition);
A loop can be terminated in the body by inserting a 'break' statement. A 'break' statement causes the execution to immediately transfer to the point following the end of the loop.
Similarly, a 'continue' statement interrupts the execution of a loop and transfer the execution to the end of the loop block.
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