javascript 如何在Javascript中编写没有'else'的IF else语句
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How to write an IF else statement without 'else' in Javascript
提问by code511788465541441
I can't use elsein my script; how can I implement an if elsestatement without using else?
我不能else在我的脚本中使用；如何在if else不使用的情况下实现语句else？
I'm trying to resize a div:
我正在尝试调整 div 的大小：
function hideTable(){
var table = document.getElementById('PDemo');
if(table.style.width == "50%") table.style.width = "150px";
if(table.style.width == "150px") table.style.width = "50%";
}
This script doesn't work because as soon as the first ifstatement is executed, the condition for the second ifstatement becomes true, so that executes too, thus nothing changes.
该脚本不起作用，因为一旦if执行第一条语句，第二条if语句的条件就变为真，因此它也执行，因此没有任何变化。
P.S. This isn't a homework. The software I am using only allows 1-line statements.
PS 这不是作业。我使用的软件只允许 1 行语句。
回答by Travis Webb
The ternary operator:
三元运算符：
condition ? execTrue() : execFalse();
This is equivalent to:
这相当于：
if (condition) {
execTrue();
}
else {
execFalse();
}
You canwrite an if/else in 1 line, just don't press enter...
您可以在 1 行中写一个 if/else，只是不要按 Enter...
if (condition) { execTrue(); } else { execFalse(); }
Further, you can write any statement of arbitrary complexity on one line:
此外，您可以在一行中编写任意复杂性的任何语句：
if(condition1) { exec1(); } else if(condition2) { exec2(); } else { execFalse() }
EDIT:I have to ask: wtf kind of horrible software only allows you to write one-line statements? Is this some form of torture? This just sounds absolutely miserable
编辑：我不得不问：wtf 那种可怕的软件只允许你写一行语句？这是某种形式的折磨吗？这听起来绝对悲惨
EDIT 2:If you're having the issue where the second if statement executes as well, you want to impose mutual exclusion, i.e., using else ifinstead of just ifon each subsequent conditional
编辑 2：如果您遇到第二个 if 语句也执行的问题，您想强加互斥，即使用else if而不是仅if在每个后续条件上
-tjw
-tjw
回答by Marcel Hymanwerth
Save the value into a different variable.
将值保存到不同的变量中。
function hideTable(){
var table = document.getElementById('PDemo');
var width = table.style.width;
if(width == "50%") table.style.width = "150px";
if(width == "150px") table.style.width = "50%";
}
回答by Sean Patrick Floyd
if(/*condition a*/){/*statements a*/}else if(/*condition b*/){/*statements b*/}else{/*statements c/*}
One line only.
只有一行。
回答by alex
If you can't use an else(and that is crazy), use a switch.
如果您不能使用 an else（这很疯狂），请使用switch.
switch (table.style.width) {
case '50%':
...
break;
case '150px':
...
break;
}
回答by Joseph Le Brech
with a while loop for the sake of uniqueness.
为了唯一性，有一个while循环。
while (!resized){
if(width == "50%") {table.style.width = "150px";resized=true;break};
if(width == "150px") table.style.width = "50%";resized=true;break};
resized=true;
}
What's the software that you are using?
你用的是什么软件？
回答by Musa
With && operator are called short-circuit operator. It will return the value of the second operand based on the value of the first operand.
与 && 运算符称为短路运算符。它将根据第一个操作数的值返回第二个操作数的值。
For example: (explanation : If 'profile' permission exist in permArray then load profile of user)
例如：（说明：如果 permArray 中存在 'profile' 权限，则加载用户的个人资料）
isPermitted(permArray,'profile') && loadProfile();
The && operator is useful also for checking for null objects before accessing their attributes. For example...
&& 运算符对于在访问它们的属性之前检查空对象也很有用。例如...
var name = person && person.getName();
