How to tell the data type

1, the first kind of typeof

Console.log (typeof undefined)//' undefined '

Console.log (typeof null)//well-known bug

Console.log (typeof True)//' Boolean '

Console.log (typeof 123)//' number '

Console.log (typeof "ABC")//' string '

Console.log (typeof function () {})//' function '

Console.log (typeof {})//' object '

Console.log (typeof [])//' object '

typeof there is a problem with the use of the TypeOf operator when using a reference type to store values there is a problem, regardless of what type of object is referenced, it returns "Object".

2, the second kind of tosring.call

Console.log (Tostring.call (123))//[object number]

Console.log (Tostring.call (' 123 '))//[object String]

Console.log (Tostring.call (undefined))//[object undefined]

Console.log (Tostring.call (True))//[object Boolean]

Console.log (Tostring.call ({}))//[object object]

Console.log (Tostring.call ([]))//[object Array]

Console.log (Tostring.call () (function () {}))//[object function]

3. The third type of instanceof

Console.log (arr instanceof Array)//true

Console.log (date instanceof date)//true

Console.log (FN instanceof Function)//True

4. Fourth Type Constructer

Console.log (Arr.constructor = = = Array)//True

Console.log (Date.constructor = = = date)//True

Console.log (Fn.constructor = = Function)//True

5. Fifth method of jquery

jquery provides a series of tool methods to determine the data type to compensate for the lack of native typeof operators for JavaScript.

The following method determines the parameters and returns a Boolean value.

Jquery.isarray (): is an array.

Jquery.isemptyobject (): Is an empty object (with no enumerable properties).

Jquery.isfunction (): is a function.

Jquery.isnumeric (): is a number.

Jquery.isplainobject (): Is the object that was generated using "{}" or "new object" instead of the object provided by the native browser.

Jquery.iswindow (): Is the Window object.

Jquery.isxmldoc (): Determines whether a DOM node is in an XML document.

How to tell the data type