What does mean n=+Number || 0

Question

I have found in HighStock js they have write a syntax like

n= +Number || 0

can anyone please expalin mean what does it mean?

Thanks

Answer 1

This is:

n= +Number || 0;

variable n will be assigned a value which should be typeof == number. If number is string then +number will be a shorthand to convert string number values to number.

So if value comes as "20", its a String value and if you prefix it with + sign then it will be converted to an Integer like 20.

Here:

n= +Number || 0;

Integer 0 will be assigned if there is no value in the var Number/or undefined.

var number = "20", nonumber;

var n = +number || 0;

$('p:eq(0)').text(n);

var o = +nonumber || 0;

$('p:eq(1)').text(o);

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<p></p>
<p></p>

Answer 2

It means if Number variable is not defined or its not numeric then assign 0 to the n variable.

Example

Example 1>
var Number = 'test';
n= +Number || 0;

O/P:
n = 0
--------------------------------------------
Example 2>
var Number = 2;
n= +Number || 0;

O/P:
n = 2
--------------------------------------------
Example 3>
n= +Number || 0;

O/P:
n = 0

Answer 3

So essentially, when you have either + or - before a variable, (ie. +Number), the variable gets cast to the type number. So either this is successful and a number is the output, or the casting fails and NaN is returned (Not a Number).

Since in most browsers Number refers to the object constructor for the type number, then the casting of it to a numerical value is not defined, and thus the result is NaN, which JavaScript interprets as a false value. Therefore:

+Number || 0 == NaN || 0 == 0

Unless Number has been defined locally and is a number (or can be casted into a number).

The following describes how each type gets casted into a number:

// Strings
+"1.12345" = 1.12345
parseFloat("1.12345") // Equivalent to

// Boolean
+True = 1
+False = 0
Number(True) // Equivalent

// Array
+[1] = NaN
// Casting fails

// Object
+{1:1} = NaN
// Casting Fails

// Undefined
+undefined = NaN
// Casting Fails

// Null
+null = 0
Number(null) // Equivalent

// Hex encoded number
+0x00FF = 255
parseInt("0x00FF", 16) // Equivalent

// Function
+function(){} = NaN
// Casting Fails