why do spaces break my code in javascript?

Question

why is el+ = v[i] different from el+=v[i] ? i thought javascript doesn't care about spacing. thanks, Any answers are appreciated it. and please don't put my question on hold. i'm here trying to learn.

var v = ['a','b','c','d','e'];
var el="";

for(i=0; i<v.length; i++){
    el+ = v[i]; // not working because of spaces, but why?
    // el+=v[i]; // working
}
document.write(el);

I am confused as to why you would think it would work. What are your trying to do? el+ is not a valid variable name and has not been defined. The NOT WORKING looks like you are trying to assign v[i] to el+ — buzzsawddog
– buzzsawddog, Commented Feb 23, 2014 at 18:24
i gave it spaces so it's easy to read. never thought, javascript read it differently. — sopanha
– sopanha, Commented Feb 23, 2014 at 18:28
Well that would be like trying to give a word spaces to make it easier to read. "A q u i c k f o x" is not easer to read than "A quick fox" As discussed below + = is not the same as +=. If you want to make it easier to read do it like this: el += v[i]; that would be allowed — buzzsawddog
– buzzsawddog, Commented Feb 23, 2014 at 18:30

spiehr · Accepted Answer · 2014-02-23 18:23:18Z

5

+= is an operator. It is not a combination of + and =.

answered Feb 23, 2014 at 18:23

spiehr

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p.s.w.g · Accepted Answer · 2014-02-23 18:24:02Z

3

Because += is an augmented (or compound) assignment operator, not + =. Similarly, i++ is fine, but i+ + causes a syntax error.

answered Feb 23, 2014 at 18:24

p.s.w.g

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Comments

Eugene P. · Accepted Answer · 2014-02-23 18:23:26Z

2

el+ =

it's illegal operator.

+=
-=
/=
*=

are available for instance

for your case. I will suggest even avoid for loop and do instead :

var el = v.join('');

answered Feb 23, 2014 at 18:23

Eugene P.

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1 Comment

buzzsawddog Over a year ago

= is a valid assignment operator the problem lies more in the fact that el+ is not a valid variable name :-)

LiverpoolsNumber9 · Accepted Answer · 2014-02-23 18:24:38Z

2

The JavaScript engine interprets "+ =" differently from "+=". That's just the way it is written.

answered Feb 23, 2014 at 18:24

LiverpoolsNumber9

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