CODEWITHSUNDEEP
javascriptobject
Damon
Damon

Reputation: 10809

In JavaScript given an object property value, can I find a corresponding property name?

I'm passing a config object with names for each slide to a function that instantiates a jQuery tools scrollable. I want the URL in the location bar to match the active tab id. I have it working so that passing the URL with the name in will navigate to the correct slide (that's at the bottom of the provided code), but I'm trying to get the URL updating when the slide changes. I know what I need to do to get that, but not how to do that, which is like in the question title.. pass a value to an object and get a property that has that value.

$(function () {
    Scrollablenav.init({
        "#tulips": 0,
        "#daffodils": 1,
        "#zebras": 2,
        "#horseshoes": 3
    });
});

Scrollablenav.init = function(config){
    var scroller = $(".scrollable").scrollable({
        circular: true,
        onSeek: function (event) {
            parent.location.hash = function(){
            //something that looks at config, sends it the value of the current slide and returns corresponding property name
            }
        }
    }).navigator({
            navi: '#slideTabs',
            naviItem: 'a',
            activeClass: 'current',
            history: true
    }).data('scrollable');

    if (!isNaN(config[location.hash])){
        scroller.seekTo(config[location.hash], 0);
     }
}

Upvotes: 0

Views: 3026

Answers (3)

Mike Christensen
Mike Christensen

Reputation: 91638

Can you change the format of your config? In other words, can we do:

$(function () {
    Scrollablenav.init({
        "#tulips": { Key: 'tulips', Index: 0 },
        "#daffodils": { Key: 'daffodils', Index: 1 },
        "#zebras": { Key: 'zebras', Index: 2 },
        "#horseshoes": { Key: 'horseshoes', Index: 3 }
    });
});

If that doesn't work, you can make a new object somewhere that maps the indexes back to the key:

var keys = {
   1: 'tulips',
   2: 'daffodils',
   3: 'zebras',
   4: 'horseshoes',
};

UPDATE:

You could also build this config dynamically:

$(function () {
    var values = ['#tulips', '#daffodils', '#zebras', '#horseshoes'];
    var config = {};

    for(var i = 0; i < values.length; i++)
    {
       config[values[i]] = { Index: i, Key: values[i] };
    }

    Scrollablenav.init(config);
});

Upvotes: 0

Tadeck
Tadeck

Reputation: 137390

You can create your own function to find property name based on its value:

function findPropertyName(object, property_value, strict) {
    if (typeof strict=='undefined'){
        strict = false;
    };
    for (property in object){
        if ((strict && object[property] === property_value) ||
            (!strict && object[property] == property_value)){
            return property;
        }
    }
    return false;
}

Function description:

  • It will return name of the first property having given value, or false if no such property has been found.
  • Third param is responsible for determining whether strict comparison should be made (eg. string "123" is equal to integer 123 - like in '123'==123, but not strictly equal - like in '123'===123).
  • Function could be improved to return all the properties having given value, but I think you do not need it.

To check the function in action see this jsfiddle.

Upvotes: 4

Evan Davis
Evan Davis

Reputation: 36592

Something like this?

function getMyHash(config, value) {
  for (item in config) {
    if (config[item] === value) {
      return item;
    }
  }
};

basically you have to iterate and match values; you can't lookup by value.

Upvotes: 2

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