我可以将字符串分配给javascript对象变量吗？

Question

This seems an easy question for experienced developer, but I did not find the answer in stack overflow.

If I declare a variable like this, var name = {};

1. I think now my name is a object?

Can I assign a string to this variable name, like name = "Foo";

2. Will this work?
3. If this work, any cons for this?

(I know I can declare name as var name = ""; But I remember in javascript, anything is object (including string, so string is also an object)).

Answer 1

JavaScript is dynamically typed language. In a nutshell, this means JS engine automatically decides what type to use depending on the type of value you are assigning to it. And it also means you can change the type of your variable anytime you want.

var name = {} //name is object

name = "" // name is now a string 

name = function (a) { return a + a } //it's now a function

The biggest con for this is that it spreads bugs:

• You can overwrite your variable unintentionally
• Type can be changed though the value will be almost the same like 1 + "" // still 1 but is not a number anymore. It's a string now 1 + "" // still 1 but is not a number anymore. It's a string now
• You can always check what type you are using with typeof() function, but it won't help you in some cases typeof( new Array() ) // is object

There are plenty of nuances you'd need to learn about dynamic typing. So much that Microsoft decided to develop TypeScript - a typed superset of JavaScript invented to make the life of JS developers easier. It can do anything JS can plus several features from strictly typed languages

Answer 2

As yBrodsky mentioned, you can do that in javascript as JS variables are not typed

you can use typeof operator to examine the type of the variable

msg = "hello";<br>
typeof msg ;
// returns "string"

msg = { a:"b"};<br>
typeof msg;                 
// returns "object"

Answer 3

Javascript is a dynamically typed language.Variable itself does not hold any datatype its the value inside the variable which defines its type.

var name = {}; // will lead to name as "object" type
name = ""; // will lead to name as "string" type
name = [] ; // will lead to name as "object" type

In Javascript, everything is not an object. There are two things primitives and natives.
These types are called primitives: null, undefined, number, string, boolean, symbol. When we do typeof primitives it will not return an object(except typeof null returns object).

Natives: String(), Number(), Boolean(), Array(), Object(), Function(), RegExp(), Date(), Error(), Symbol(). When we do typeof natives then it will return an object.

Native are created with the new keyword:

var hey = new String("rajat");

And new will always return an object.