js--小结⑤
2015-06-24 18:23
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js中的for循环,while循环,do...while循环和C语言的一模一样
有几个问题要提醒一下的是
1. null是对象,即object undefined是undefined
demo
结果:
2.几个demo
break的标签引用
do-while
结果:
while
结果
:
for
结果
:
break
continue
结果:
有几个问题要提醒一下的是
1. null是对象,即object undefined是undefined
demo
<!DOCTYPE html> <html> <body> <p id="demo"></p> <script> document.getElementById("demo").innerHTML = typeof undefined + "<br>" + typeof null + "<br>" + (null === undefined) + "<br>" + (null == undefined); </script> </body> </html>
结果:
2.几个demo
break的标签引用
<!DOCTYPE html> <html> <body> <script> 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>"); } </script> </body> </html>
do-while
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Document</title> </head> <body> <p>点击下面的按钮,主要i小于5就一直循环代码块</p> <button onclick="myFunction()">hit me</button> <p id="demo"></p> <script> function myFunction() { var x="",i=0; do{ x=x+"The number is " +i+ "<br />"; i++; } while(i<5) document.getElementById("demo").innerHTML=x; } </script> </body> </html>
结果:
while
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Document</title> </head> <body> <p>点击下面的按钮,只要i小于5就一直循环代码块</p> <button onclick="myFunction()">hit me</button> <p id="demo"></p> <script> function myFunction() { var x="",i=0; while(i<5) { x=x+"The number is " +i+ "<br />"; i++; } document.getElementById("demo").innerHTML=x; } </script> </body> </html>
结果
:
for
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Document</title> </head> <body> <script> cars=["BMW","Volvo","Saab","Ford"]; var i=0; for(;cars[i];) { document.write(cars[i]+"<br />"); i++; } </script> </body> </html>
结果
:
break
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Document</title> </head> <body> <p>点击按钮,测试带有break语句的循环</p> <button onclick="myFunction()">hit me</button> <p id="demo"></p> <script> function myFunction() { var x="",i=0; for(i=0;i<10;i++) { if(i==3) { break; } x=x+"The numbe is "+i+ "<br />"; } document.getElementById("demo").innerHTML=x; } </script> </body> </html>
continue
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Document</title> </head> <body> <p>点击下面的按钮来执行循环,该循环会跳过i=3的步进</p> <button onclick="myFunction()">hit me</button> <p id="demo"></p> <script> function myFunction() { var x="",i=0; for(i=0;i<10;i++) { if(i==3) { continue; } x=x+"the numeber is "+i +"<br />"; document.getElementById("demo").innerHTML=x; } } </script> </body> </html>
结果:
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