A simple way to determine data type using js

Everyone who knows js knows that there is a typeof used to determine various data types. There are two ways of writing: typeof xxx , typeof(xxx)

The following example:

typeof 2 Output number

typeof null Output object

typeof {} Output object

typeof [] Output object

typeof (function(){}) Output function

typeof undefined Output undefined

typeof '222' Output string

typeof true Output boolean

This contains five data types in js number string boolean undefinedobject and functionType function

You will definitely ask when you see this: How do I distinguish between object, array and null?

Next We use another tool: Object.prototype.toString.call

This is a native prototype extension function of the object, used to distinguish data types more accurately.

Let’s try this thing:

var gettype=Object.prototype.toString

gettype.call('aaaa') Output [object String]

gettype.call(2222) Output [object Number]

gettype.call(true) Output [object Boolean]

gettype.call(undefined ) Output [object Undefined]

gettype.call(null) Output [object Null]

gettype.call({}) Output [object Object]

gettype.call ([]) Output [object Array]

gettype.call(function(){}) Output [object Function]

Seeing this, we have solved the problem just now.

In fact, there are many type judgments in js

[object HTMLpElement] p object,

[object HTMLBodyElement] body object,

[object Document](IE) or

[object HTMLDocument](firefox,google)...

Various dom nodes judgment, these things will be used when we write plug-ins.

The methods that can be encapsulated are as follows:

var  gettype=Object.prototype.toString

var  utility={

isObj:function(o){

    return  gettype.call(o)=="[object Object]";

 },

     isArray:function(o){

        return  gettype.call(o)=="[object Array]";

     },

     isNULL:function(o){

        return  gettype.call(o)=="[object Null]";

     },

     isDocument:function(){

        return  gettype.call(o)=="[object Document]"|| [object HTMLDocument];

     }

     ........

}

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