if...else
Misol
Agar soat 20 dan kichik bo‘lsa, "Good day" ni chiqaring:
let hour = new Date().getHours();
if (hour < 20) {
document.getElementById("demo").innerHTML = "Good day";
}
O‘zingiz sinab ko‘ring »
"Good day" yoki "Good evening" ni chiqaring:
let hour = new Date().getHours();
if (hour < 20) {
greeting = "Good day";
} else {
greeting = "Good evening";
}
O‘zingiz sinab ko‘ring »
Quyida ko‘proq misollar.
Tavsif
if/else operatori belgilangan shart true bo‘lsa, kod blokini bajaradi. Agar shart false bo‘lsa, boshqa kod blokini bajarish mumkin.
if/else operatori JavaScript’ning "shartli" operatorlari tarkibiga kiradi; ular turli shartlarga qarab turli amallarni bajarish uchun ishlatiladi.
JavaScript’da quyidagi shartli operatorlar mavjud:
- Belgilangan shart true bo‘lsa bajariladigan kod blokini ko‘rsatish uchun if operatoridan foydalaning
- Xuddi shu shart false bo‘lsa bajariladigan kod blokini ko‘rsatish uchun else operatoridan foydalaning
- Birinchi shart false bo‘lsa, tekshiriladigan yangi shartni ko‘rsatish uchun else if operatoridan foydalaning
- Bajariladigan ko‘plab kod bloklaridan birini tanlash uchun switch operatoridan foydalaning
Sintaksis
if operatori shart true bo‘lsa bajariladigan kod blokini belgilaydi:
if (condition) {
// block of code to be executed if the condition is true
}
else operatori shart false bo‘lsa bajariladigan kod blokini belgilaydi:
if (condition) {
// block of code to be executed if the condition is true
} else {
// block of code to be executed if the condition is false
}
else if operatori birinchi shart false bo‘lsa, yangi shartni belgilaydi:
if (condition1) {
// block of code to be executed if condition1 is true
} else if (condition2) {
// block of code to be executed if the condition1 is false and condition2 is true
} else {
// block of code to be executed if the condition1 is false and condition2 is false
}
Parametr qiymatlari
| Parametr | Tavsif |
|---|---|
| condition | Majburiy. true yoki false qiymatga ega bo‘ladigan ifoda |
Ko‘proq misollar
Agar vaqt 10:00 dan kam bo‘lsa, "Good morning" salomlashuvini, aks holda, vaqt 20:00 dan kam bo‘lsa, "Good day" salomlashuvini, aks holda "Good evening" salomlashuvini yarating:
var time = new Date().getHours();
if (time < 10) {
greeting = "Good morning";
} else if (time < 20) {
greeting = "Good day";
} else {
greeting = "Good evening";
}
O‘zingiz sinab ko‘ring »
Agar hujjatdagi birinchi <div> elementining id’si "myDIV" bo‘lsa, uning font-size qiymatini o‘zgartiring:
var x = document.getElementsByTagName("DIV")[0];
if (x.id === "myDIV") {
x.style.fontSize = "30px";
}
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Foydalanuvchi rasm ustiga bossa, <img> elementining source atributi (src) qiymatini o‘zgartiring:
<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>
O‘zingiz sinab ko‘ring »
Foydalanuvchi kiritgan ma’lumotga qarab xabar ko‘rsating:
var letter = document.getElementById("myInput").value;
var text;
// If the letter is "c"
if (letter === "c") {
text = "Spot on! Good job!";
// If the letter is "b" or "d"
} else if (letter === "b" || letter === "d") {
text = "Close, but not close enough.";
// If the letter is anything else
} else {
text = "Waaay off..";
}
O‘zingiz sinab ko‘ring »
Kiritilgan ma’lumotlarni tekshiring (validatsiya qiling):
var x, text;
// Get the value of the input field with id="numb"
x = document.getElementById("numb").value;
// If x is Not a Number or less than 1 or greater than 10, output "input is not valid"
// If x is a number between 1 and 10, output "Input OK"
if (isNaN(x) || x < 1 || x > 10) {
text = "Input not valid";
} else {
text = "Input OK";
}
O‘zingiz sinab ko‘ring »
Tegishli sahifalar
JavaScript darsligi: JavaScript if...else operatorlari
JavaScript darsligi: JavaScript switch operatori
Brauzerlarda qo‘llab-quvvatlash
if...else — ECMAScript1 (JavaScript 1997) imkoniyati.
U barcha brauzerlarda qo‘llab-quvvatlanadi:
| Chrome | Edge | Firefox | Safari | Opera |
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