What does = +

I was wondering what the = +_ operator means in JavaScript. It looks like it does assignments.

Example:

hexbin.radius = function(_) {
   if (!arguments.length)
       return r;
   r = +_;
   dx = r * 2 * Math.sin(Math.PI / 3);
   dy = r * 1.5;
   return hexbin;
};

r = +_;

Example:

+"1"

cast "1" to pure number 1.

var _ = "1";
var r = +_;

r is now 1 , not "1" .

Moreover, according to the MDN page on Arithmetic Operators:

The unary plus operator precedes its operand and evaluates to its operand but attempts to converts it into a number, if it isn't already . [...] It can convert string representations of integers and floats, as well as the non-string values true , false , and null . Integers in both decimal and hexadecimal ( "0x" -prefixed) formats are supported. Negative numbers are supported (though not for hex). If it cannot parse a particular value, it will evaluate to NaN .

It is also noted that

unary plus is the fastest and preferred way of converting something into a number

It is not an assignment operator.

hexbin.radius = function(_) {
                //       ^ It is passed here
    // ...
};

DO NOT CONFUSE IT WITH += operator

=+ are actually two operators = is assignment and + and _ is variable name.

like:

i = + 5;
or 
j = + i;
or 
i = + _;

My following codes will help you to show use of =+ to convert a string into int.
example:

y = +'5'
x = y +5
alert(x);

outputs 10

use: So here y is int 5 because of =+
otherwise:

y = '5'
x = y +5
alert(x);

outputs 55

Where as _ is a variable.

_ = + '5'
x = _ + 5
alert(x)

outputs 10

Additionally, It would be interesting to know you could also achieve same thing with ~ (if string is int string (float will be round of to int))

y = ~~'5'  // notice used two time ~
x = y  + 5
alert(x);

also outputs 10

~ is bitwise NOT : Inverts the bits of its operand. I did twice for no change in magnitude.

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