How to use Knockout observables in i18next?

Question

I\'m trying to somehow dynamically use i18next translations together with Knockout.js, but I cant figure out how.

Neither a custom Knockout binding or the i18next jQ

Answer 1

KO config:

var language = ko.observable('');

ko.i18n = function(key) {
  return ko.computed(function() {
    if (language() != null) {
      return i18n.t(key, {
        lng : language()
      });
    } else {
      return "";
    }
  }, key);
};

view-model:

var labels = {      
aboutUs: ko.i18n('app:labels.aboutUs'), 
contactUsBtn: ko.i18n('app:labels.contactUsBtn') }

view:

<span data-bind="text: labels.aboutUs">

Answer 2

I'm not very familiar with i18next, so I might be using i18next incorrectly, but you could easily achieve this by creating a bindingHandler. A very simple version of such a bindingHandler, which supports passing optional options, could look like:

ko.bindingHandlers['translatedText'] = {
    update: function(element, valueAccessor, allBindings){
        var key = ko.unwrap(valueAccessor());
        var options = ko.toJS(allBindings.get('translationOptions') || {});
        var translation = i18n.t(key, options);
        element.innerText = translation;
    }
};

Given the following i18next initialization code:

i18n.init({
    lng: "en",
    debug: true,
    resStore: {
        en: {
            translation: {
                'myTextKey': 'My translated value is "__value__"',
                'otherTextKey': 'This is just a text which does not use options'
            }
        }
    }
});

You could use it with the following HTML:

<input type="text" data-bind="value: input, valueUpdate: 'afterkeydown'"/>
<div data-bind="translatedText: 'myTextKey', translationOptions: { value: input }"></div>
<div data-bind="translatedText: 'otherTextKey'"></div>

And the following view model:

function ViewModel(){
    this.input = ko.observable();
}

ko.applyBindings(new ViewModel);

I have saved the above code to a jsfiddle which you can find at http://jsfiddle.net/md2Hr/

Answer 3

I've updated the code to support translating HTML attributes as well.

Here is a working demo: http://jsfiddle.net/remisture/GxEGe/

HTML

<label>HTML/text</label>
<textarea data-bind="i18n: 'key', i18n-options: {var: input}"></textarea>
<label>Attribute</label>
<input type="text" data-bind="i18n: '[placeholder]key', i18n-options: {var: input}" />

JS

define(['knockout', 'i18next'], function (ko, i18n) {
    ko.bindingHandlers.i18n = {
        update: function (element, valueAccessor, allBindings) {
            var key = ko.unwrap(valueAccessor()),
                options = ko.toJS(allBindings.get('i18n-options') || {}),
                translation,
                parts,
                attr;

            // Check whether we are dealing with attributes
            if (key.indexOf('[') === 0) {
                parts = key.split(']');
                key = parts[1];
                attr = parts[0].substr(1, parts[0].length - 1);
            }

            translation = i18n.t(key, options);

            if (attr === undefined) {
                // Check whether the translation contains markup
                if (translation.match(/<(\w+)((?:\s+\w+(?:\s*=\s*(?:(?:"[^"]*")|(?:'[^']*')|[^>\s]+))?)*)\s*(\/?)>/)) {
                    //noinspection InnerHTMLJS
                    element.innerHTML = translation;
                } else {
                    // Check whether the translation contains HTML entities
                    if (translation.match(/&(?:[a-z]+|#x?\d+);/gi)) {
                        //noinspection InnerHTMLJS
                        element.innerHTML = translation;
                    } else {
                        // Treat translation as plain text
                        element.innerText = translation;
                    }
                }
            } else {
                // Add translation to given attribute
                element.setAttribute(attr, translation);
            }
        }
    };
});

Answer 4

Thanks for a great example, @robert.westerlund!

I slightly modified your example to better fit my needs:

ko.bindingHandlers['i18n'] = {
        update: function (element, valueAccessor, allBindings) {
            var key = ko.unwrap(valueAccessor()),
                options = ko.toJS(allBindings.get('i18n-options') || {}),
                translation = i18next.t(key, options);

            // Check whether the translation contains markup
            if (translation.match(/<(\w+)((?:\s+\w+(?:\s*=\s*(?:(?:"[^"]*")|(?:'[^']*')|[^>\s]+))?)*)\s*(\/?)>/)) {
                element.innerHTML = translation;
            } else {
                // Check whether the translation contains HTML entities
                if (translation.match(/&(?:[a-z]+|#x?\d+);/gi)) {
                    element.innerHTML = translation;
                } else {
                    // Treat translation as plain text
                    element.innerText = translation;
                }
            }
        }
    };