// file name: demo.html
<! DOCTYPE html >
< html> < head> < meta charset = " UTF-8" > < title> 练习</ title> < style> #myCanvas { box-shadow : 6px 9px 80px 13px rgba ( 0, 0, 0, .65) ; margin : 50px 400px; } </ style> </ head> < body> < canvas id = " myCanvas" width = " 500" height = " 500" > </ canvas> </ body> < script src = " js/demo.js" > </ script>
</ html>
var myCanvas = document. getElementById ( "myCanvas" ) ;
var ctx = myCanvas. getContext ( "2d" ) ; ctx. translate ( 250 , 250 ) ;
ctx. beginPath ( ) ;
ctx. arc ( 0 , 0 , 20 , 0 , Math. PI * 2 , false ) ;
ctx. closePath ( ) ;
ctx. strokeStyle = "red" ;
ctx. stroke ( ) ;
var starAngle = 0 ; for ( var i = 0 ; i < 12 ; i++ ) { ctx. save ( ) ; ctx. rotate ( starAngle) ; starAngle += Math. PI / 12 ; ctx. beginPath ( ) ; ctx. moveTo ( 0 , - 100 ) ; ctx. quadraticCurveTo ( - 40 , 0 , 0 , 100 ) ; ctx. fillStyle = "green" ; ctx. fill ( ) ; ctx. beginPath ( ) ; ctx. moveTo ( 0 , - 100 ) ; ctx. quadraticCurveTo ( 40 , 0 , 0 , 100 ) ; ctx. fillStyle = "green" ; ctx. fill ( ) ; ctx. restore ( ) ;
} var starAngle = 0 ;
for ( var i = 0 ; i < 12 ; i++ ) { ctx. save ( ) ; ctx. rotate ( starAngle) ; starAngle += Math. PI / 12 ; ctx. beginPath ( ) ; ctx. moveTo ( 0 , - 100 ) ; ctx. quadraticCurveTo ( - 40 , 0 , 0 , 100 ) ; ctx. strokeStyle = "red" ; ctx. stroke ( ) ; ctx. beginPath ( ) ; ctx. moveTo ( 0 , - 100 ) ; ctx. quadraticCurveTo ( 40 , 0 , 0 , 100 ) ; ctx. strokeStyle = "red" ; ctx. stroke ( ) ; ctx. restore ( ) ;
}