js-02- loop

Loop classification {

　　for

　　while

　　do ( ) while

}

A, for loop and the nested for loop

　　for round robin format eg:

<script>
    var sim = 0;
    for(var i=1;i<=100;i++){
        sum+=i;
}
        console.log(sum)

</script>

　　The expression "i = 1" total run 1, run before the loop;

　　 The expression "i <= 100" determines whether a condition is satisfied iteration of the loop, if so, how many times the loop is executed many times, out of the loop body is not satisfied;

　　 The expression "i ++" self-increment operator.

　　for nested loop eg:

< Script > 
    for ( var I = . 1 ; I <= . 3 ; I ++ ) { 
        document.write ( ' outer loop of the loop ' + I + ' result times <br /> ' );
             for ( var J = . 1 ; J <= 2 ; J ++ ) { 
                document.write ( ' inner loop cycle ' + J + ' times results <br /> ' );  
            }
        document.write ( ' <HR /> ' );
 </ Script > 

// once the outer loop, the inner loop a

Two, the while loop EG ( first determination condition, and then performs content loop )

<Script> 
    var = I. 1; // initial value 
        while (i <= 20) { // condition 
            document.write (I); 
　　　　　　　document.write ( '<br />'); 
          I = + 10; 
}   
</ Script > 
// output value is 1; 11;

Three, do () while loop eg ( performed first in the do, and then determine the conditions, conditions continue to cycle, not recycled when conditions are not met )

do{
	document.write('hello meizi');
   }while(false);

Four, break and continue

　　a: break: break out of this loop, the current loop ends, the loop performed behind the statement;

　　b: continue: continue to cycle out of the current to continue the next cycle;

Guess you like