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JavaScript - Constructor Property

The constructor property returns the constructor function for all JavaScript variables and shows their data type.


document.getElementById("demo1").innerHTML =
"john".constructor + "<br /> +
(3.14).constructor + "<br />" +
false.constructor + "<br />" +
[1,2,3,4].constructor + "<br />" +
{name:'john', age:34}.constructor + "<br />" +
new Date().constructor + "<br />" +
function () {}.constructor;
hello

 

You can check the constructor property to find out if an object is an Array (contains the word "Array"). 


var myArray = ["bob","james"];
function isArray(myArray)
{
    return myArray.constructor.toString().indexOf("Array") > -1;
}
$("#demo2").html(isArray(myArray));

 

You can check the constructor property to find out if an object is an Array (contains the word "Date").


var myDate = new Date();
function isDate(myDate)
{
    return myDate.constructor.toString().indexOf("Date") > -1;
}
$("#demo3").html(isDate(myDate));

https://www.w3schools.com/jsref/jsref_constructor_string.asp
https://www.w3schools.com/jsref/jsref_constructor_array.asp