Question

How do we return the datatype of arguments without using type of in javascript

Answer 1

The alternative way of typeof operator is Object.prototype.toString.

This is a method that prints out the name of the class that you passed into toString.

JavaScript has seven primitive data types and Object: boolean, null, undefined, number, BigInt, string, symbol and object.

You can use below code to check the data type of each arguments.

Javascript code:-

function checkType(val){
return Object.prototype.toString.call(val).slice(8,-1);
}

console.log(checkType('Test'));
console.log(checkType(1));
console.log(checkType(undefined));
console.log(checkType(true));
console.log(checkType([1,2,3]));
console.log(checkType({}));
console.log(checkType(null));

output:-

• "String"
• "Number"
• "Undefined"
• "Boolean"
• "Array"
• "Object"
• "Null"

Code Summary:

In above code we created function checkType() that returns a data type of a given arguments and we are printing the output of that using console.log() method.

Note Object.prototype.toString.call() return a result in format [Object object], e.g. [Object Number]. So just to have a Number as output we are slicing the result using slice method.

Output in console:-