Js Objects | Table O Contents

Two separate primitives with the same value and type will be declared equal as true in Javascript …

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Hint. Objects are passed by reference only, and not by value …

Rule. Primitives such as numbers and strings are passed as individual values.

Therefore, mixing value types inside of an object is permissable.

Mixing Value types

For, example …

var universa = {state: 'Florida', name: 'Florida Southern', enrollment: '10,000'};

In the above universa Object variable, the key enrollment represents a number value type.

Whereas, the state key represents a string value type.


Because an Object variable is actually spawned by the built-in Object Class, the now var object universa may call the methods of its parent Class using dot notation, as follows:


;where isCamelCase is an exposed function of the built-in Object Class.


The properties of the var object universa may also be called with dot notation substituting the value of each property for the name of the function in the above example, as follows:


;where the value of the property enrollment is returned, as follows:


Function Values

When constructing your Object variable, mixing and matching value types is agreeable to the underlying Javascript interpreter.

For example, rather than a normal value of type String, or a numeric value of type Number, why not try a method value of type Function?

Just plug your function code into one of the placeholders of your Object variable, as follows:

run: function() {console.log('go fast!')}};

The Code

// Declare and initialize a constant named `num` with a value of 42
const num = 42;

// Declare and initialize a constant named `anotherNum` with a value of 42
const anotherNum = 42;


// Compare the two primitives (numbers)
// console.log(num === anotherNum);
// Returns `true`

// Compare the two primitives (strings)
// console.log(`hello there` === `hello there`);
// Returns `true`


// Rule. Objects are NOT primitives.
// Primitives cannot be assigned properties.

// Declare an object w an empty array
const obj = {};

// Declare a second object w a different name, but similar content
const anotherObj = {};

// Pass the pointer to the value of the obj to another object named anotherObj // anotherObj = {obj};

The Test B

// Compare the two objects
// console.log(Obj === anotherObj);
// Returns `false`

// Set the value of the `a` property of the object `anotherObj` to the number 1 
anotherObj.a = 1;

// Note. Because objects are passed by reference only, and not by value ...
// Passing another object to an object as a perceived value will NOT result in a value of `true`
// Two objects when compared will always show `false`.

console.log('another obj', anotherObj);
console.log('obj', obj);

Last Subtitle

More to come …

Note. The above synopsis was derived from a video lecture written, produced and performed by …

Reed Barger: [1].

For additional reference on the topic of Objects see the Mozilla Developer Network: [2]

For a working Internet development platform for Javascript Primitives see Scrimba: [3]

  1. Javascript: The Complete Developer, 2020

  2. Mozilla Developer Network

  3. Scrimba Javascript Developer Platform


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