var id = id++;
console.log(id);
I just wonder why this isn't work? I put it inside a function, I was expecting it start from 2, and then increment 1 by 1. But in the console what I see is NaN. Why?
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var id = id++; (id++? before id is available ?,so id = undefined )internals-in– internals-in2013-12-07 12:06:16 +00:00Commented Dec 7, 2013 at 12:06
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6 Answers
Unless you initialize a variable (=assign some value to it), its value is undefined and undefined++ is not a number (NaN).
Comments
id is undefined, undefined++ is NaN.
You are using a variable which is not defined before, so NaN is the answer.
Comments
You are not assigning any value to id.
You need to initialize it.
Try:
var id = 1;
id++;
console.log(id);
Comments
Didn't you mean?
var id = 1;
id++;
console.log(id);
Comments
You can't increment something that isn't already defined. So undefined ++ is NaN.
Comments
The problem was that you didn't asign a value to "id" variable, so first you need to declare and initialize a variable, then you can manipulate it's value.
var id; //declare
id = 1; //initialize;
id += 1 or id++ //manipulate it(increment the value with 1);
or shorter:
var id = 1;
id++;
