如何检查对象是否为数组? [英] How to check if an object is an array?

问题描述

我正在尝试编写一个接受字符串列表或单个字符串的函数.如果它是一个字符串，那么我想将其转换为仅包含一项的数组，因此我可以遍历它而不必担心出现错误.

I'm trying to write a function that either accepts a list of strings, or a single string. If it's a string, then I want to convert it to an array with just the one item, so I can loop over it without fear of an error.

那么如何检查变量是否为数组?

So how do I check if the variable is an array?

我已经整理了以下各种解决方案，并创建了 jsperf测试.它们都很快速，因此只需使用Array.isArray即可-它是得到良好支持的现在和跨框架工作.

I've rounded up the various solutions below and created a jsperf test. They're all fast, so just use Array.isArray -- it's well-supported now and works across frames.

推荐答案

ECMAScript标准中提供的用于查找Object类的方法是使用Object.prototype中的toString方法.

The method given in the ECMAScript standard to find the class of Object is to use the toString method from Object.prototype.

if( Object.prototype.toString.call( someVar ) === '[object Array]' ) {
    alert( 'Array!' );
}

或者您可以使用typeof来测试它是否为字符串:

Or you could use typeof to test if it is a String:

if( typeof someVar === 'string' ) {
    someVar = [ someVar ];
}

或者如果您不关心性能，则可以对新的空数组执行concat.

Or if you're not concerned about performance, you could just do a concat to a new empty Array.

someVar = [].concat( someVar );

还有可以直接查询的构造函数:

There's also the constructor which you can query directly:

if (somevar.constructor.name == "Array") {
    // do something
}

---

从彻底处理 ://stackoverflow.com/users/157247/tj-crowder> @TJ Crowder的博客(在下面的评论中发布).

---

Check out a thorough treatment from @T.J. Crowder's blog, as posted in his comment below.

查看以下基准，以了解哪种方法效果更好:

Check out this benchmark to get an idea which method performs better: http://jsben.ch/#/QgYAV

从 @Bharath 使用Es6将字符串转换为数组，以解决以下问题:

From @Bharath convert string to array using Es6 for the question asked:

const convertStringToArray = (object) => {
   return (typeof object === 'string') ? Array(object) : object 
}

假设:

let m = 'bla'
let n = ['bla','Meow']
let y = convertStringToArray(m)
let z = convertStringToArray(n)
console.log('check y: '+JSON.stringify(y)) . // check y: ['bla']
console.log('check y: '+JSON.stringify(z)) . // check y: ['bla','Meow']

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