I want take some JSON values and make variable from them, but when I do it I get an error. In first stage JSON array is empty, thats why I used if != null, but even with filled array I get an error.

var tempJS=[];  
$("#sth td").each(function(){
    $this = $(this);
    tempJS.push({"COLOR":$this.attr("data-color"),});
});
console.log(JSON.stringify(tempJS));

if(tempJS!=null) var kolor=tempJS[c-1].COLOR;

Why is the last line giving me the following error:

Uncaught TypeError: Cannot read property 'COLOR' of undefined

I want take some JSON values and make variable from them, but when I do it I get an error. In first stage JSON array is empty, thats why I used if != null, but even with filled array I get an error.

var tempJS=[];  
$("#sth td").each(function(){
    $this = $(this);
    tempJS.push({"COLOR":$this.attr("data-color"),});
});
console.log(JSON.stringify(tempJS));

if(tempJS!=null) var kolor=tempJS[c-1].COLOR;

Why is the last line giving me the following error:

Uncaught TypeError: Cannot read property 'COLOR' of undefined

• javascript
• json

Share Improve this question Follow edited Aug 2, 2014 at 7:01 Hugo Dozois 8,4281212 gold badges5555 silver badges5959 bronze badges asked Aug 2, 2014 at 1:11 snuuvesnuuve 31511 gold badge44 silver badges1414 bronze badges 1

• The error is very explicit, what is undefined is tempJS[c-1], where is that "c" on the code?, beside you are checking that tempJS is not null, it assigning tempJS[c-1], you should check for the same thing – Lu Roman Commented Aug 2, 2014 at 1:20

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2 Answers 2

Sorted by: Reset to default 3

If you try on the console:

[]==null
> false

you'll see that returns false. This means that if you check if the array equals null you will always get a false, and always run the code in the if statement.

You should do this instead:

if(tempJS.length) var kolor=tempJS[c-1].COLOR;

You don't need if(tempJS.length > 0) because every number is treated like true except 0 that means false.

A zero-length array is not same as null. Try testing if (tempJS.length > 0) ...