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var b = "pp.specifications.full_specs."; var c = arr[i];

here the value of arr[i] is Memory

var a = b+c; console.log(a);

it prints pp.specifications.full_specs.Memory on console

but when I use

console.log(pp.specifications.full_specs.Memory);

then prints an json object as:

{ Series: 'Inspiron', Model: 'A562103SIN9', Utility: 'Everyday Use', OS: 'Windows 10 Home (64-bit)', Dimensions: '274.73 x 384.9 x 25.44 mm', Weight: '2.62 Kg', Warranty: '1 Year Onsite Warranty' }

whenever the value of a contains pp.specifications.full_specs.Memory;

So what is the reason for getting different outputs?

Sarthak Agarwal
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1 Answers1

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There's a elementary difference between

console.log(pp.specifications.full_specs.Memory);

and

console.log("pp.specifications.full_specs.Memory");

Note the quotes!

So the expression: console.log(pp.specifications.full_specs.Memory); can be read from left to right:

Print to the output value of pp.specifications.full_specs.Memory and this is a value of pp object after taking its property specifications and then its property full_specs etc.

And the "pp.specifications.full_specs.Memory" means only a piece of text.

What is happening in your code should now be clearer:

// B is piece of text
var b = "pp.specifications.full_specs.";
// C is some other value - let's say also textual one
var c = arr[i]
// So b+c will mean add text to some other text
// It's expected that the result of such operations is concatenated text
// So then console.log(b+c) will mean
// Print the concatenated text from b and c
// And it's just plain text
console.log(b+c);

//It's the same as:
console.log("pp.specifications.full_specs.Memory");

// And this one means print some specific object attributes
// which is different operation!
console.log(pp.specifications.full_specs.Memory);

If you want to access objects by text you can do the following:

var d = eval(b+c);

It's pretty dangerous and eval should be avoided but I just wanted to demonstrate the basic idea. Eval executes strings as if they were code. So string "pp.specifications.full_specs.Memory" will be evaluates (yep!) as value of the actual object.

As The eval can execute anything it should be always avoided and moreover it's superslow!

Instead if you want to access some property of pp basic on some text input you can do:

pp['specifications']['full_specs']['Memory']

As the pp.x notation is equivalent to expression: pp['x']

I hope my answer will help you understand Javascript mechanisms better :)

Piotr Styczyński
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