JavaScript if/else hukun ceesu

定义和用法

If/else hukun ceesu ke aiki domin samar boko ceesu idan hukun za a rarraba ke da haliya. Idan hukun ke da matsakaici, a zai aiki domin boko ceesu na tsaki.

If/else hukun ceesu wani ɗaya daga ɗaukar hukun ceesu na JavaScript, wanda ke aiki domin aiki na daban don haliyar daban.

A cikin JavaScript, a have hukun ceesu da suka bayan:

  • A samu if domin samar boko ceesu, idan hukun da za a rarraba ke da haliya.
  • A samu else domin samar boko ceesu, idan hukun da yake a matsakaici ke da matsakaici.
  • Idan hukun farko ke da matsakaici, a samu else if domin samar hukun tsaki na jini a hanyar.
  • A samu switch domin samar boko ceesu kananan wanda za a rarraba a hanyar.

实例

Idan lokaci na wuri (HOUR) ya kai 20:00, a cikin abin da id="demo" a hanyar "Good day":

var time = new Date().getHours(); 
ka da {
  document.getElementById("demo").innerHTML = "Good day";
}

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Kuduwar hanyar ceesu TIY a cikin tsaki na rafin.

语法

If hukun ceesu, a boko ceesu wanda ke a haliya ceesu:

ka da {condition) {
  // kungiya na koda a zai aiki idan condition yana da alama
}

ka da {

ka da {
  // kungiya na koda a zai aiki idan condition yana da alama
} else { 
  // kungiya na koda a zai aiki idan condition yana da alama
}

Idan kuma condition1 yana da alama, ka bayyana kuma condition else if:

ka da {
  // kungiya na koda a zai aiki idan condition1 yana da alama
ka da {
  // kungiya na koda a zai aiki idan condition1 yana da kuma condition2 yana da alama
} else {
  // kungiya na koda a zai aiki idan condition1 yana da kuma condition2 yana da alama
}

Wuri na arg

Arg Ba'amurko
condition Wajib. Wuri ce ta hanyar kiyaye da cewa wuri ne true ko false.

Tafiyar hanyar

Bolani JavaScript: ECMAScript 1

Kudiwar kula

实例

Idan wakilin aya 20:00, bu ka tsara kira "Good day", amma idan baya, bu ka tsara kira "Good evening":

var time = new Date().getHours(); 
ka da {
  greeting = "Good day";
} else {
  greeting = "Good evening";
}

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实例

Idan wakilin aya 10:00, bu ka tsara kira "Good morning", amma idan kuma wakilin aya 20:00, bu ka tsara kira "Good day", kuma idan baya, bu ka tsara kira "Good evening":

var time = new Date().getHours(); 
ka da {
  greeting = "Good morning";
ka da {
  greeting = "Good day";
} else {
  greeting = "Good evening";
}

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实例

Idan gida na <div> na farko a cikin dokumentin yana "myDIV", sabunta koko fariya sa:

var x = document.getElementsByTagName("DIV")[0];
if (x.id === "myDIV") {}} 
  x.style.fontSize = "30px";
}

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实例

当用户单击图像，更改 <img> 元素的源属性 (src) 的值：

<img id="myImage" onclick="changeImage()" src="pic_bulboff.gif" width="100" height="180">
<script>
function changeImage() {
  var image = document.getElementById("myImage");
  if (image.src.match("bulbon")) {
    image.src = "pic_bulboff.gif";
  } else {
    image.src = "pic_bulbon.gif";
  }
}
</script>

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实例

根据用户输入显示消息：

var letter = document.getElementById("myInput").value;
var text;
// 如果字母为 "c"
if (letter === "c") {
  text = "Spot on! Good job!";
// 如果字母为 "b" 或 "d"
} else if (letter === "b" || letter === "d") {
  text = "Close, but not close enough.";
// 如果是其他字母
} else {
  text = "Waaay off..";
}

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实例

验证输入数据：

var x, text;
// 获取 id="numb" 的输入字段的值
x = document.getElementById("numb").value;
// 如果 x 不是数字或小于 1 或大于 10，则输出 "input is not valid"
// 如果 x 是 1 到 10 之间的数字，则输出 "Input OK"
if (isNaN(x) || x < 1 || x > 10) {
  text = "Input not valid";
} else {
  text = "Input OK";
}

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browser supports

cibiyu Chrome IE Firefox Safari Opera
if/else 支持 支持 支持 支持 支持

相关页面

JavaScript 教程：JavaScript If...Else 语句

JavaScript 教程：JavaScript Switch ɗanarorin