check javascript array value is not empty

Question

I am a little confused with checking if an array value us empty from a json response.

{
  "status": "success",
  "message": "All pages re-ordered",
  "content": {
    "_wysihtml5_mode": "1",
    "Page": {
        "title": "cover",
        "page_text": "dfvdfvdfvdfvdv story go daddy xxx",
        "storyborad_img": "1jhkjh.png",
        "background_url": "kjbj.png",
        "newBackground_url": "",
        "text_font": "arial",
        "id": "30",
        "book_id": "38",
        "newStoryborad_img": {
            "name": "1jhkjh.png",
            "type": "image\/png",
            "tmp_name": "\/Applications\/MAMP\/tmp\/php\/phpvyf8Xx",
            "error": 0,
            "size": 185607
        }
    },
    "User": {
        "username": "testuser"
    }
  }
}

I have tried to check typeof array == undefined and .length but both give me what is in the else statement newBackground_url

var page = $.parseJSON(xhr.responseText.replace('</p>', ''));
var imageType;
if(page.content.Page.newStoryborad_img.length > 0) {
    imageType = page.content.Page.newStoryborad_img.name;
}
else {
    imageType = page.content.Page.newBackground_url.name;
}

Why is there a </p> in your JSON? The path should be page.content.Page.storyborad_img [sic] according to your code. — tadman
– tadman, Commented Jun 17, 2014 at 21:48
</p> was part of the response, but I am changing it around so will remove that once I have the code refactored. — Keith Power
– Keith Power, Commented Jun 17, 2014 at 21:51
'Storyborad' reminded me of kazakhstana.files.wordpress.com/2011/09/borat-swimsuit.jpg — Niels Keurentjes
– Niels Keurentjes, Commented Jun 17, 2014 at 21:51
Isn't newStoryborad_img an object? Or, do you receive an array when there are more than one images? — Jack
– Jack, Commented Jun 17, 2014 at 21:55
typeof(array) == undefined should give you the else statement, because you have defined it in your json. You might want typeof(array) != 'undefined' if you want its presence to trigger the if block. (which is what it looks like you want it to do) — JTG
– JTG, Commented Jun 17, 2014 at 21:59

JTG · Accepted Answer · 2014-06-17 22:12:14Z

2

It depends. According to your example, you are returning an object "newStoryborad_img": {...}

In which case you would want to use typeof(page.content.Page.newStoryborad_img) != 'undefined'

Demo typeof: http://jsfiddle.net/gunderjt/cn2cs/

But if you are looking at having an array of objects "newStoryborad_img": [{...}] (notice the brackets). Then to check the presence of any objects in the array (assuming you are returning an empty array)

page.content.Page.newStoryborad_img.length > 0 will be what you want

Demo length: http://jsfiddle.net/gunderjt/cn2cs/1/

answered Jun 17, 2014 at 22:12

JTG

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2 Comments

Keith Power Over a year ago

thanks for the help. If I change "newStoryborad_img": "" I get if instead of else for the typeof. I will always be passing newStoryborad_img either empty or with values

Nick Blexrud Over a year ago

@KeithPower, and this is an update to @JTG's answer/fiddle, change the if statement condition to typeof(page.content.Page.newStoryborad_img) != 'string' meaning it's an object or anything else that is not a string, then console.log if. If it's a string i.e. "", then console.log else. JS Fiddle

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