strange behavior with ternary operator

Question

I tried to program a function, that converts javascript objects to a http-compatible string. I achieved what I intendet to do, but I don't know why it works. My final function is:

function paramify (p) {
    var n = 0, r = "";
    for (var i in p) {
        r+=(n++==0?"":"&")+i+"="+p[i];
    }
    return r;
}

The version without the ternary operator is:

function paramify (p) {
    var n=0, r="";
    for(var i in p){
        if(n++!=0){
            r+="&"
        }
        r+=i+"="+p[i]
    }
    return r;
}

Example json-object:

{"authToken":"aqsd2","username":"test","password":"1234"}

will become:

authToken=aqsd2&username=test&password=1234

(as intendet)

May somebody explain me, why this works? I didn't expect n++ to become 0 when n is already 0.

Your'e using post increment, the value of `n` will be used in the comparison, and after that the increment is done. — Teemu, Oct 20 '13 at 19:24
Always put spaces for readability e.g. your expression should be written as `r += (n++ == 0? "": "&") + i + "=" +p[i];` — Grijesh Chauhan, Oct 20 '13 at 19:25
Just to clarify, the version with the ternary is equivalent to the if version. Are you getting different outputs? — bfavaretto, Oct 20 '13 at 19:26
No, I just added the non-ternary version, because I thought some people might not know that operator. — Florian Wendelborn, Oct 20 '13 at 19:27

score 3 · Accepted Answer · edited May 23 '17 at 12:05

3

It's the difference between pre and post increment. It's explained in this question: ++someVariable Vs. someVariable++ in Javascript

edited May 23 '17 at 12:05

Community

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answered Oct 20 '13 at 19:26

Rengers

14,911
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score 3 · Answer 2 · answered Oct 20 '13 at 19:29

3

"variable++" is incremented after being evaluated, "++variable" is incremented before being evaluated. Same goes for the "--" operator.

reference at http://msdn.microsoft.com/en-us/library/ie/26k41698(v=vs.94).aspx

answered Oct 20 '13 at 19:29

dav1dsm1th

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strange behavior with ternary operator

2 Answers2