教材来自<<菜鸟学堂>>
条件语句
//-------------------------------------- if (time<20) { x="Good day"; } //-------------------------------------- if (time<20) { x="Good day"; } else { x="Good evening"; } //-------------------------------------- if (time<10) { x="Good morning"; } else if (time>=10 && time<20) { x="Good day"; } else { x="Good evening"; }
switch 语句
var d=new Date().getDay(); switch (d) { case 1: x="今天是星期一"; break; case 2: x="今天是星期二"; break; case 3: x="今天是星期三"; break; case 4: x="今天是星期四"; break; case 5: x="今天是星期五"; break; case 6: x="今天是星期六"; break; default: x="周末快乐"; }
for 循环
for (var i=0,len=cars.length; i<len; i++){ document.write(cars[i] + "<br>"); } //-------------------------------------- var i=2,len=cars.length; for (; i<len; i++){ document.write(cars[i] + "<br>"); } //-------------------------------------- var i=0,len=cars.length; for (; i<len; ){ document.write(cars[i] + "<br>"); i++; }
For/In 循环
var person={fname:"John",lname:"Doe",age:25}; for (x in person){ txt=txt + person[x]; }
while 循环
while (i<5){ x=x + "The number is " + i + "<br>"; i++; } //-------------------------------------- do{ x=x + "The number is " + i + "<br>"; i++; }while (i<5);
比较 for 和 while
cars=["BMW","Volvo","Saab","Ford"];var i=0; for (;cars[i];){ document.write(cars[i] + "<br>"); i++; } //-------------------------------------- cars=["BMW","Volvo","Saab","Ford"]; var i=0; while (cars[i]){ document.write(cars[i] + "<br>"); i++; }
Break 语句
for (i=0;i<10;i++){ if (i==3) break; x=x + "The number is " + i + "<br>"; }
Continue 语句
for (i=0;i<=10;i++){ if (i==3) continue; x=x + "The number is " + i + "<br>"; }
标签
continue 语句(带有或不带标签引用)只能用在循环中。
break 语句(不带标签引用),只能用在循环或 switch 中。
通过标签引用,break 语句可用于跳出任何 JavaScript 代码块:
cars=["BMW","Volvo","Saab","Ford"]; list: { document.write(cars[0] + "<br>"); document.write(cars[1] + "<br>"); document.write(cars[2] + "<br>"); break list; document.write(cars[3] + "<br>"); document.write(cars[4] + "<br>"); document.write(cars[5] + "<br>"); }