boards/static/js/form.js

var ITEM_FILE_SOURCE = 'fileSource';

$('input[name=image]').wrap($('<div class="file_wrap"></div>'));

$('body').on('change', 'input[name=image]', function(event) {
    var file = event.target.files[0];

    if(file.type.match('image.*')) {
        var fileReader = new FileReader();

        fileReader.addEventListener("load", function(event) {
            var wrapper = $('.file_wrap');

            wrapper.find('.file-thumb').remove();
            wrapper.append(
                $('<div class="file-thumb" style="background-image: url('+event.target.result+')"></div>')
            );
        });

        fileReader.readAsDataURL(file);
    }
});

var form = $('#form');
$('textarea').keypress(function(event) {
    if ((event.which == 10 || event.which == 13) && event.ctrlKey) {
        form.find('input[type=submit]').click();
    }
});

$('#preview-button').click(function() {
    var data = {
        raw_text: $('textarea').val()
    }

    var diffUrl = '/api/preview/';

    $.post(diffUrl,
        data,
        function(data) {
            var previewTextBlock = $('#preview-text');
            previewTextBlock.html(data);
            previewTextBlock.show();
        })
});

/**
 * Show text in the errors row of the form.
 * @param form
 * @param text
 */
function showAsErrors(form, text) {
    form.children('.form-errors').remove();

    if (text.length > 0) {
        var errorList = $('<div class="form-errors">' + text + '<div>');
        errorList.appendTo(form);
    }
}

function addHiddenInput(form, name, value) {
    form.find('input[name=' + name + ']').val(value);
}

function selectFileChoice() {
    var file_input = $('#id_file');
    var url_input = $('#id_file_url');

    var file_input_row = file_input.parent().parent();
    var url_input_row = url_input.parent().parent();

    file_input_row.toggle();
    url_input_row.toggle();
    url_input.val('');
    file_input.val('');

    var source;
    if (file_input_row.is(':visible')) {
        source = 'file';
    } else {
        source = 'url';
    }
    localStorage.setItem(ITEM_FILE_SOURCE, source);
}

$(document).ready(function() {
    var powDifficulty = parseInt($('body').attr('data-pow-difficulty'));
    if (powDifficulty > 0 && typeof SharedWorker != 'undefined') {
        var worker = new SharedWorker($('.post-form').attr('data-pow-script'));
        worker.port.onmessage = function(e) {
            var form = $('#form');
            addHiddenInput(form, 'timestamp', e.data.timestamp);
            addHiddenInput(form, 'iteration', e.data.iteration);
            addHiddenInput(form, 'guess', e.data.guess);

            form.submit();
            $('.post-form-w').unblock();
        };
        worker.onerror = function(event){
            throw new Error(event.message + " (" + event.filename + ":" + event.lineno + ")");
        };
        worker.port.start();

        var form = $('#form');
        var submitButton = form.find('input[type=submit]');
        submitButton.click(function() {
            showAsErrors(form, gettext('Computing PoW...'));
            $('.post-form-w').block({ message: gettext('Computing PoW...') })

            var msg = $('textarea').val().trim();

            var data = {
                msg: msg,
                difficulty: parseInt($('body').attr('data-pow-difficulty')),
                hasher: $('.post-form').attr('data-hasher')
            };
            worker.port.postMessage(data);

            return false;
        });
    }

    var $fileSourceButton = $('#file-source-button');
    if (window.localStorage) {
        var source = localStorage.getItem(ITEM_FILE_SOURCE);
        if (source == null) {
            source = 'file';
        }
        if (source == 'file') {
            $('#id_file_url').parent().parent().hide();
        } else {
            $('#id_file').parent().parent().hide();
        }

        $fileSourceButton.click(function() {
            selectFileChoice();
        });
    } else {
        $fileSourceButton.hide();
    }
});