boards/static/js/form.js

$('input[name=image]').wrap($('<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 == 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);
}

$(document).ready(function() {
    var powDifficulty = parseInt($('body').attr('data-pow-difficulty'));
    if (powDifficulty > 0) {
        var worker = new Worker($('#powScript').attr('src'));
        worker.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();
            form.find('input[type=submit]').toggle();
        };

        var form = $('#form');
        var submitButton = form.find('input[type=submit]');
        submitButton.click(function() {
            showAsErrors(form, gettext('Computing PoW...'));
            submitButton.toggle();

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

            var data = {
                msg: msg,
                difficulty: parseInt($('body').attr('data-pow-difficulty')),
                hasher: $('#sha256Script').attr('src')
            };
            worker.postMessage(data);

            return false;
        });
    }
});