JavaScript judgment variable data type

The data type in JS
1. Numeric (number): Includes integers, floating-point numbers.
2. Boolean Type (Boolean)
3. String type
4. Objects (object)
5. Arrays (Array)
6. Null value (NULL)
7. Undefined (Undefined)

Two
1. Numeric type (number)
The more common methods of judging are:

function Isnumber (val) {
Return typeof val = = = ' number ';
}

2. Judging the variable Val is not a Boolean type

Function Isbooleantype (val) {
Return typeof val = = = "Boolean";
}

3. Determine if a variable is a string type

Function Isstringtype (val) {
Return typeof val = = = "string";
}

4. Determine if the variable is undefined

Function Isundefined (val) {
Return typeof val = = = "undefined";
}

5. Determine if the variable is not an object

function Isobj (str) {
if (str = = = NULL | | typeof str = = = ' undefined ') {
return false;
}
return typeof str = = = ' object ';
}

6. Determine if the variable is not NULL

Function IsNull (val) {
return val = = = NULL;
}

7. Determine if the variable arr is an array

Method One
function IsArray (arr) {
return Object.prototype.toString.apply (arr) = = = ' [Object Array] ';
}

Method Two
function IsArray (arr) {
if (arr = = = NULL | | typeof arr = = = ' undefined ') {
return false;
}
return Arr.constructor = = = Array;
}

JavaScript judgment variable data type