如何在 JavaScript 中确定一个数字是否为奇数
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How to determine if a number is odd in JavaScript
提问by Jannie Theunissen
Can anyone point me to some code to determine if a number in JavaScript is even or odd?
谁能指出一些代码来确定 JavaScript 中的数字是偶数还是奇数？
回答by Chii
Use the below code:
使用以下代码：
function isOdd(num) { return num % 2;}
console.log("1 is " + isOdd(1));
console.log("2 is " + isOdd(2));
console.log("3 is " + isOdd(3));
console.log("4 is " + isOdd(4));1 represents an odd number, while 0 represents an even number.
1代表奇数，0代表偶数。
回答by 0x499602D2
Use the bitwise ANDoperator.
使用按位运算AND符。
function oddOrEven(x) {
return ( x & 1 ) ? "odd" : "even";
}
function checkNumber(argNumber) {
document.getElementById("result").innerHTML = "Number " + argNumber + " is " + oddOrEven(argNumber);
}
checkNumber(17);<div id="result" style="font-size:150%;text-shadow: 1px 1px 2px #CE5937;" ></div>If you don't want a string return value, but rather a boolean one, use this:
如果你不想要一个字符串返回值，而是一个布尔值，使用这个：
var isOdd = function(x) { return x & 1; };
var isEven = function(x) { return !( x & 1 ); };
回答by TNC
You could do something like this:
你可以这样做：
function isEven(value){
if (value%2 == 0)
return true;
else
return false;
}
回答by CloudyMarble
function isEven(x) { return (x%2)==0; }
function isOdd(x) { return !isEven(x); }
回答by Isaac Fife
Do I have to make an array really large that has a lot of even numbers
我是否必须制作一个非常大的数组，它有很多偶数
No. Use modulus (%). It gives you the remainder of the two numbers you are dividing.
否。使用模数 (%)。它为您提供要除的两个数字的余数。
Ex. 2 % 2 = 0 because 2/2 = 1 with 0 remainder.
Ex2. 3 % 2 = 1 because 3/2 = 1 with 1 remainder.
Ex3. -7 % 2 = -1 because -7/2 = -3 with -1 remainder.
This means if you mod any number x by 2, you get either 0 or 1 or -1. 0 would mean it's even. Anything else would mean it's odd.
这意味着如果您将任何数字 x 乘以 2，您将得到 0 或 1 或 -1。0 表示它是偶数。其他任何事情都意味着它很奇怪。
回答by s0d4pop
This can be solved with a small snippet of code:
这可以通过一小段代码解决：
function isEven(value) {
if (value%2 == 0)
return true;
else
return false;
}
Hope this helps :)
希望这可以帮助 ：）
回答by pb2q
Like many languages, Javascript has a modulus operator %, that finds the remainder of division. If there is no remainder after division by 2, a number is even:
像许多语言一样，Javascript 有一个模运算符%，它可以找到除法的余数。如果除以 2 后没有余数，则数字为偶数：
// this expression is true if "number" is even, false otherwise
(number % 2 == 0)
This is a very common idiom for testing for even integers.
这是测试偶数的一个非常常见的习惯用法。
回答by Katia Punter
With bitwise, codegolfing:
使用按位，codegolfing：
var isEven=n=>(n&1)?"odd":"even";
回答by dgh
A simple function you can pass around. Uses the modulo operator %:
您可以传递的简单函数。使用模运算符%：
var is_even = function(x) {
return !(x % 2);
}
is_even(3)
false
is_even(6)
true
回答by Abdennour TOUMI
Use my extensions :
使用我的扩展：
Number.prototype.isEven=function(){
return this % 2===0;
};
Number.prototype.isOdd=function(){
return !this.isEven();
}
then
然后
var a=5;
a.isEven();
==False
==假
a.isOdd();
==True
==真
if you are not sure if it is a Number , test it by the following branching :
如果您不确定它是否为 Number ，请通过以下分支进行测试：
if(a.isOdd){
a.isOdd();
}
UPDATE :
更新 ：
if you would not use variable :
如果您不使用变量：
(5).isOdd()
Performance :
表现 ：
It turns out that Procedural paradigm is better than OOP paradigm . By the way , i performed profiling in this FIDDLE. However , OOP way is still prettiest .
事实证明，过程范式优于面向对象范式。顺便说一下，我在这个 FIDDLE 中进行了 分析。但是，OOP 方式仍然是最漂亮的。
