javascript 中的类型检查
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type checking in javascript
提问by sova
How can I check if a variable is currently an integer type? I've looked for some sort of resource for this and I think the === operator is important, but I'm not sure how to check if a variable is an Integer (or an Array for that matter)
如何检查变量当前是否为整数类型？我为此寻找了某种资源，我认为 === 运算符很重要，但我不确定如何检查变量是否为整数（或与此相关的数组）
回答by Quentin
A variable will never be an integer type in JavaScript — it doesn't distinguish between different types of Number.
JavaScript 中的变量永远不会是整数类型——它不区分不同类型的 Number。
You can test if the variable contains a number, and if that number is an integer.
您可以测试变量是否包含数字，以及该数字是否为整数。
(typeof foo === "number") && Math.floor(foo) === foo
If the variable might be a string containing an integer and you want to see if that is the case:
如果变量可能是一个包含整数的字符串，并且您想查看是否是这种情况：
foo == parseInt(foo, 10)
回答by dat
These days, ECMAScript 6 (ECMA-262) is "in the house". Use Number.isInteger(x)to ask the question you want to ask with respect to the type of x:
现在，ECMAScript 6 (ECMA-262) 已经“在家里”了。用Number.isInteger(x)问你要问关于x的类型的问题：
js> var x = 3
js> Number.isInteger(x)
true
js> var y = 3.1
js> Number.isInteger(y)
false
回答by kennebec
A number is an integer if its modulo %1 is 0-
如果一个数字的模 %1 是 0-，则该数字是一个整数
function isInt(n){
return (typeof n== 'number' && n%1== 0);
}
This is only as good as javascript gets- say +- ten to the 15th.
这仅与 javascript 一样好 - 比如说 +- 10 到 15 日。
isInt(Math.pow(2,50)+.1)returns true, as does
Math.pow(2,50)+.1 == Math.pow(2,50)
isInt(Math.pow(2,50)+.1)返回true，就像
Math.pow(2,50)+.1 == Math.pow(2,50)
回答by Dan
I know you're interested in Integer numbers so I won't re answer that but if you ever wanted to check for Floating Point numbers you could do this.
我知道你对整数感兴趣，所以我不会再回答这个问题，但如果你想检查浮点数，你可以这样做。
function isFloat( x )
{
return ( typeof x === "number" && Math.abs( x % 1 ) > 0);
}
Note: This MAY treat numbers ending in .0(or any logically equivalent number of 0's) as an INTEGER. It actually needs a floating point precision error to occur to detect the floating point values in that case.
注意：这可以将以.0（或任何逻辑上等效的0's数）结尾的数字视为整数。在这种情况下，它实际上需要发生浮点精度错误来检测浮点值。
Ex.
前任。
alert(isFloat(5.2)); //returns true
alert(isFloat(5)); //returns false
alert(isFloat(5.0)); //return could be either true or false
回答by eSniff
Try this code:
试试这个代码：
alert(typeof(1) == "number");
回答by Chris West
Quite a few utility libraries such as YourJSoffer functions for determining if something is an array or if something is an integer or a lot of other types as well. YourJS defines isIntby checking if the value is a number and then if it is divisible by 1:
相当多的实用程序库（例如YourJS）提供了用于确定某物是数组还是整数或许多其他类型的函数。YourJS通过检查值是否为数字以及是否可以被 1 整除来定义isInt：
function isInt(x) {
return typeOf(x, 'Number') && x % 1 == 0;
}
The above snippet was taken from this YourJS snippetand thusly only works because typeOfis defined by the library. You can download a minimalistic version of YourJS which mainly only has type checking functions such as typeOf(), isInt()and isArray(): http://yourjs.com/snippets/build/34,2
上面的代码片段取自这个 YourJS 代码片段，因此只能工作，因为它typeOf是由库定义的。你可以下载一个简约版的YourJS，它主要只有类型检查功能，例如typeOf()，isInt()和isArray()：http: //yourjs.com/snippets/build/34,2
回答by vitalets
You may also have a look on Runtyper- a tool that performs type checking of operands in ===(and other operations).
For your example, if you have strict comparison x === yand x = 123, y = "123", it will automatically check typeof x, typeof yand show warning in console:
您还可以查看Runtyper- 一种对操作数===（和其他操作）执行类型检查的工具。
对于您的示例，如果您有严格的比较x === yand x = 123, y = "123"，它将自动检查typeof x, typeof y并在控制台中显示警告：
Strict compare of different types: 123 (number) === "123" (string)
不同类型的严格比较：123（数字）===“123”（字符串）
