break循环
首先i=0，判断i是否<=5,满足条件，判断i是否等于3，i不等于3，输出i=0，i的值加1，判断i是否<=5，判断i是否等于3，i不等于3，输出i=1，i的值加1，判断i是否<=5，判断i是否等于3，i不等于3，输出i=2，i的值加1，判断i是否<=5，判断i是否等于3，i等于3，跳出循环，结束
<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><meta http-equiv="X-UA-Compatible" content="IE=edge"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>Document</title>
</head>
<body><script>for(var i=0;i<=5;i++){if(i===3){break}console.log(i)}</script>
</body>
</html> 
continue
i=0，判断i<=5,判断i是否等于3，不等于，输出i=0,i=i+1,
判断i<=5,判断i是否等于3，不等于,输出i=1，i=i+1,
判断i<=5,判断i是否等于3，不等于,输出i=2，i=i+1,
判断i<=5,判断i是否等于3，i等于3，跳过，之后的代码都不执行，i=i+1,
判断i<=5,判断i是否等于3，i不等于3，输出i=4，i=i+1,
判断i<=5,i等于5，结束
<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><meta http-equiv="X-UA-Compatible" content="IE=edge"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>Document</title>
</head>
<body><script>for(var i=0;i<=5;i++){if(i===3){continue}console.log(i)}</script>
</body>
</html> 