文章目录  41 嵌套的for循环 42 for循环嵌套练习(1) 43 for循环嵌套练习(2) 44 break和continue 45 质数练习补充   
 
<! DOCTYPE  html > < html> < head> < title> </ title> < metacharset  =  " utf-8" > < scripttype = " text/javascript" > for ( var  i =  0 ;  i <  5 ;  i++ ) { for ( var  j =  0 ;  j <  5 ;  j++ ) { document. write ( "*  " ) ; } document. write ( "<br>" ) ; } for ( var  i =  1 ;  i <=  5 ;  i++ ) { for ( var  j =  1 ;  j <=  i;  j++ ) { document. write ( "*  " ) ; } document. write ( "<br>" ) ; } for ( var  i =  5 ;  i >=  1 ;  i-- ) { for ( var  j =  1 ;  j <=  i;  j++ ) { document. write ( "*  " ) ; } document. write ( "<br>" ) ; } </ script> < style> 
 </ style> </ head> < body> </ body> </ html> <! DOCTYPE  html > < html> < head> < title> </ title> < metacharset  =  " utf-8" > < scripttype = " text/javascript" > for ( var  i =  1 ;  i <=  9 ;  i++ ) { for ( var  j =  1 ;  j <=  i;  j++ ) { document. write ( "<span>"  +  j +  "*"  +  i +  "="  +  ( j *  i)  +  "</span>"  ) ; } document. write ( "<br>" ) ; } 
</ script> < style> body  { width :  2000px; } span  { display :  inline-block; width :  80px; } 
</ style> </ head> < body> </ body> </ html> <! DOCTYPE  html > < html> < head> < title> </ title> < metacharset  =  " utf-8" > < scripttype = " text/javascript" > for ( var  i =  2 ;  i <=  100 ;  i++ ) { var  flag =  1 ; for ( var  j =  2 ;  j <=  parseInt ( i **  0.5 ) ;  j++ ) { if ( i %  j ==  0 ) { flag =  0 ; break ; } } if ( flag) { document. write ( i +  " " ) ; } } 
</ script> < style> 
 </ style> </ head> < body> </ body> </ html> <! DOCTYPE  html > < html> < head> < title> </ title> < metacharset  =  " utf-8" > < scripttype = " text/javascript" > for ( var  i =  0 ;  i <  5 ;  i++ ) { console. log ( i) ; break ; } if ( true ) { break ; console. log ( i) ; } outer : for ( var  i =  0 ;  i <  5 ;  i++ ) { console. log ( "外层循环" ) ; for ( var  j =  0 ;  j <  5 ;  j++ ) { break  outer; console. log ( "内层循环" ) ; 		} } for ( var  i =  0 ;  i <  5 ;  i++ ) { console. log ( i) ; if ( i ==  2 ) { continue ; } } console. time ( "test" ) ; for ( var  i =  0 ;  i <  1000000 ;  i++ ) { for ( var  j =  0 ;  j <  i;  j++ ) { } } console. timeEnd ( "test" ) ; 
</ script> < style> 
 </ style> </ head> < body> </ body> </ html> <! DOCTYPE  html > < html> < head> < title> </ title> < metacharset  =  " utf-8" > < scripttype = " text/javascript" > for ( var  i =  2 ;  i <=  100 ;  i++ ) { var  flag =  1 ; for ( var  j =  2 ;  j <=  Math. sqrt ( i) ;  j++ ) { if ( i %  j ==  0 ) { flag =  0 ; break ; } } if ( flag) { document. write ( i +  " " ) ; } } var  result =  Math, sqrt ( 4 ) ;  
</ script> < style> 
 </ style> </ head> < body> </ body> </ html>