I want to know why after running the third line of code the result of a is 5?
a = 10;
b = 5;
a =+ b;
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2the correct syntax is a+=b; a=+b; is not correct. it is simply assigning b value to a.Anil– Anil2012-04-15 09:42:16 +00:00Commented Apr 15, 2012 at 9:42
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Possible duplicate of What is the purpose of a plus symbol before a variable?Ivar– Ivar2018-12-17 12:40:54 +00:00Commented Dec 17, 2018 at 12:40
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2 Answers
Awkward formatting:
a =+ b;
is equivalent to:
a = +b;
And +b is just a fancy way of casting b to number, like here:
var str = "123";
var num = +str;
You probably wanted:
a += b;
being equivalent to:
a = a + b;
answered Apr 15, 2012 at 9:20
Tomasz Nurkiewicz
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3 Comments
gotofritz
...while a += b is a shortcut for a = a + b, which is probably what you want
Tomasz Nurkiewicz
@fritzfromlondon: Thanks for pointing that out, I allowed myself to add your comment to an answer to better stand out
Felix Kling
The + sign before the function, actually called Unary plus and is part of a group called a Unary Operators and (the Unary Plus) is used to convert string and other representations to numbers (integers or floats).
A unary operation is an operation with only one operand, i.e. a single input. This is in contrast to binary operations, which use two operands.
Basic Uses:
const x = "1";
const y = "-1";
const n = "7.77";
console.log(+x);
// expected output: 1
console.log(+n);
// expected output: 7.77
console.log(+y);
// expected output: -1
console.log(+'');
// expected output: 0
console.log(+true);
// expected output: 1
console.log(+false);
// expected output: 0
console.log(+'hello');
// expected output: NaNWhen the + sign is positioned before a variable, function or any returned string representations the output will be converted to integer or float; the unary operator (+) converts as well the non-string values true, false, and null.
