Javascript - Check if key exists in object

Question

I'm building a object in Javascript to parse the uri contents and attach their key / value pairs to it. However, I'm stuck on how to find out if a key exists. Here's the code :

var uri = {
    segments : {},
    parse : function() {
        var segments = {};
        var parts;
        var s;

        parts = location.href.split('/');
        parts = parts[3].split('?');
        parts = parts[1].split('&');

        for (var i = 0; i < parts.length; i++) {
            s = parts[i].split('=');
            segments[s[0]] = s[1];
        }

        uri.segments = segments;

        return segments;
    },
    segment : function(key) {
        if (uri.segments.length == 0)
        {
            uri.parse();
        }

        /* before was 'key in uri-segments' */      
        if (Object.prototype.hasOwnProperty.call(uri.segments, key))
        {
            return uri.segments[key];
        }
        else
        {
            return false
        }
    },
};

edit : full code

@amnotiam For example, imagine a key called toString. 'toString' in {} is true.` — Rob W
– Rob W, Commented Mar 10, 2012 at 22:14
@RobW: By uri contents, I would assume that specific keys are used for the different parts. Unless perhaps it's going to separate out the querystring parameters into keys. — user1106925
– user1106925, Commented Mar 10, 2012 at 22:17
@yoda The uri will never be parsed, because uri.segments.length == undefined (it is not an array). undefined == 0 is false. — Rob W
– Rob W, Commented Mar 10, 2012 at 22:21
@RobW Thank you, I failed to see that. Changed it to segments : [] and it worked :) — yoda
– yoda, Commented Mar 10, 2012 at 22:29

Rob W · Accepted Answer · 2012-03-10 22:12:16Z

7

Use the hasOwnProperty method to check whether a key exists or not:

// hasOwnProperty from the objects prototype, to avoid conflicts
Object.prototype.hasOwnProperty.call(uri.segments, key);
//                                   ^ object      ^ key

answered Mar 10, 2012 at 22:12

Rob W

350k87 gold badges811 silver badges683 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

yoda Over a year ago

It says the key doesn't exist, but If I call it directly it displays the right result.

Collectives™ on Stack Overflow

Javascript - Check if key exists in object

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related