Javascript type check implementation code _ javascript skills

One way to check the object type is to refer to a common property called constructor of all JavaScript objects. This attribute is a reference to a function originally used to construct this object. The Code is as follows:

// Check whether our number is actually a string
If (num. constructor = String)
// If yes, parse it into numbers
Num = parseInt (num );
// Check whether our string is actually an array
If (str. constructor = Array)
// If yes, use a comma to connect to the array to obtain a string
Str = str. join (',');

Table 1 shows the results of performing type checks on different types of objects using the two methods described above. The first column of the table shows the objects we are trying to find. Run typeof Variable (Variable is the value shown in the first column ). All results in this column are strings. Finally, the third column shows the result of running Variable. constructor on the objects contained in the first column. All the results in these columns are objects.

Table 1. Variable type check

-------------------------------
Variable typeof Variable. constructor
-------------------------------
{An: "object"} object Object
["An", "array"] object Array
Function () {} function Function
"A string" string String
55 number
True boolean Boolean
New User () object User
----------------------------------

Using a variable's constructor as an object type reference may be the simplest type check method. When you want to determine the exact number of parameters to be passed into your function, strict type checks may be helpful.