Javascript 如何在javascript中的if语句中指定多个条件
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How to specify multiple conditions in an if statement in javascript
提问by adilahmed
Here is how I mention two conditions if this or this
这是我如何提到两个条件，如果这个或这个
if (Type == 2 && PageCount == 0) || (Type == 2 && PageCount == '')
PageCount= document.getElementById('<%=hfPageCount.ClientID %>').value;
}
回答by AlanFoster
just add them within the main bracket of the if statement like
只需将它们添加到 if 语句的主括号中，例如
if ((Type == 2 && PageCount == 0) || (Type == 2 && PageCount == '')) {
PageCount= document.getElementById('<%=hfPageCount.ClientID %>').value;
}
Logically this can be rewritten in a better way too! This has exactly the same meaning
从逻辑上讲，这也可以用更好的方式重写！这具有完全相同的含义
if (Type == 2 && (PageCount == 0 || PageCount == '')) {
回答by Edward Taylor
I am currently checking a large number of conditions, which becomes unwieldy using the if statement method beyond say 4 conditions. Just to share a clean looking alternative for future viewers... which scales nicely, I use:
我目前正在检查大量条件，使用超过 4 个条件的 if 语句方法变得笨拙。只是为了为未来的观众分享一个干净的替代品......它很好地扩展，我使用：
var a = 0;
var b = 0;
a += ("condition 1")? 1 : 0; b += 1;
a += ("condition 2")? 1 : 0; b += 1;
a += ("condition 3")? 1 : 0; b += 1;
a += ("condition 4")? 1 : 0; b += 1;
a += ("condition 5")? 1 : 0; b += 1;
a += ("condition 6")? 1 : 0; b += 1;
// etc etc
if(a == b) {
//do stuff
}
回答by Glen Thompson
Here is an alternative way to do that.
这是一种替代方法。
const conditionsArray = [
condition1,
condition2,
condition3,
]
if (conditionsArray.indexOf(false) === -1) {
"do somthing"
}
Or ES6
或者 ES6
if (!conditionsArray.includes(false)) {
"do somthing"
}
回答by user40521
Sometimes you can find tricks to further combine statments.
有时您可以找到进一步组合语句的技巧。
Like for example:
例如：
0 + 0 = 0
and
和
"" + 0 = 0
so
所以
PageCount == 0
PageCount == ''
can be written like:
可以写成：
PageCount+0 == 0
In javascript 0is just as good as falseinverting !it would turn 0into true
在JavaScript0是一样好false反相!，将转0成true
!PageCount+0
for a grand total of:
总计：
if ( Type == 2 && !PageCount+0 ) PageCount = elm.value;
回答by Fabrizio Calderan
the whole ifshould be enclosed in brackets and the oroperator is ||an not !!, so
整个if应该用括号括起来，or运算符是||not !!，所以
if ((Type == 2 && PageCount == 0) || (Type == 2 && PageCount == '')) { ...
回答by vaske
if((Type == 2 && PageCount == 0) || (Type == 2 && PageCount == '')) {
PageCount= document.getElementById('<%=hfPageCount.ClientID %>').value;
}
This could be one of possible solutions, so 'or' is || not !!
这可能是可能的解决方案之一，所以 'or' 是 || 不是 ！！
回答by Sergio Tulentsev
Wrap them in an extra pair of parens and you're good to go.
将它们包裹在一对额外的括号中，您就可以开始了。
if((Type == 2 && PageCount == 0) || (Type == 2 && PageCount == ''))
PageCount= document.getElementById('<%=hfPageCount.ClientID %>').value;
}
回答by Lilcent
function go(type, pageCount) {
if ((type == 2 && pageCount == 0) || (type == 2 && pageCount == '')) {
pageCount = document.getElementById('<%=hfPageCount.ClientID %>').value;
}
}
