placeholders.js

/* 
 * The MIT License
 *
 * Copyright (c) 2012 James Allardice
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), 
 * to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, 
 * and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

// Defines the global Placeholders object along with various utility methods
(function (global) {

    "use strict";

    // Cross-browser DOM event binding
    function addEventListener(elem, event, fn) {
        if (elem.addEventListener) {
            return elem.addEventListener(event, fn, false);
        }
        if (elem.attachEvent) {
            return elem.attachEvent("on" + event, fn);
        }
    }

    // Check whether an item is in an array (we don't use Array.prototype.indexOf so we don't clobber any existing polyfills - this is a really simple alternative)
    function inArray(arr, item) {
        var i, len;
        for (i = 0, len = arr.length; i < len; i++) {
            if (arr[i] === item) {
                return true;
            }
        }
        return false;
    }

    // Move the caret to the index position specified. Assumes that the element has focus
    function moveCaret(elem, index) {
        var range;
        if (elem.createTextRange) {
            range = elem.createTextRange();
            range.move("character", index);
            range.select();
        } else if (elem.selectionStart) {
            elem.focus();
            elem.setSelectionRange(index, index);
        }
    }

    // Attempt to change the type property of an input element
    function changeType(elem, type) {
        try {
            elem.type = type;
            return true;
        } catch (e) {
            // You can't change input type in IE8 and below
            return false;
        }
    }

    // Expose public methods
    global.Placeholders = {
        Utils: {
            addEventListener: addEventListener,
            inArray: inArray,
            moveCaret: moveCaret,
            changeType: changeType
        }
    };

}(this));

(function (global) {

    "use strict";

    var validTypes = [
            "text",
            "search",
            "url",
            "tel",
            "email",
            "password",
            "number",
            "textarea"
        ],

        // The list of keycodes that are not allowed when the polyfill is configured to hide-on-input
        badKeys = [

            // The following keys all cause the caret to jump to the end of the input value
            27, // Escape
            33, // Page up
            34, // Page down
            35, // End
            36, // Home

            // Arrow keys allow you to move the caret manually, which should be prevented when the placeholder is visible
            37, // Left
            38, // Up
            39, // Right
            40, // Down

            // The following keys allow you to modify the placeholder text by removing characters, which should be prevented when the placeholder is visible
            8, // Backspace
            46 // Delete
        ],

        // Styling variables
        placeholderStyleColor = "#ccc",
        placeholderClassName = "placeholdersjs",
        classNameRegExp = new RegExp("(?:^|\\s)" + placeholderClassName + "(?!\\S)"),

        // These will hold references to all elements that can be affected. NodeList objects are live, so we only need to get those references once
        inputs, textareas,

        // The various data-* attributes used by the polyfill
        ATTR_CURRENT_VAL = "data-placeholder-value",
        ATTR_ACTIVE = "data-placeholder-active",
        ATTR_INPUT_TYPE = "data-placeholder-type",
        ATTR_FORM_HANDLED = "data-placeholder-submit",
        ATTR_EVENTS_BOUND = "data-placeholder-bound",
        ATTR_OPTION_FOCUS = "data-placeholder-focus",
        ATTR_OPTION_LIVE = "data-placeholder-live",
        ATTR_MAXLENGTH = "data-placeholder-maxlength",

        // Various other variables used throughout the rest of the script
        test = document.createElement("input"),
        head = document.getElementsByTagName("head")[0],
        root = document.documentElement,
        Placeholders = global.Placeholders,
        Utils = Placeholders.Utils,
        hideOnInput, liveUpdates, keydownVal, styleElem, styleRules, placeholder, timer, form, elem, len, i;

    // No-op (used in place of public methods when native support is detected)
    function noop() {}

    // Avoid IE9 activeElement of death when an iframe is used.
    // More info:
    // http://bugs.jquery.com/ticket/13393
    // https://github.com/jquery/jquery/commit/85fc5878b3c6af73f42d61eedf73013e7faae408
    function safeActiveElement() {
        try {
            return document.activeElement;
        } catch (err) {}
    }

    // Hide the placeholder value on a single element. Returns true if the placeholder was hidden and false if it was not (because it wasn't visible in the first place)
    function hidePlaceholder(elem, keydownValue) {
        var type,
            maxLength,
            valueChanged = (!!keydownValue && elem.value !== keydownValue),
            isPlaceholderValue = (elem.value === elem.getAttribute(ATTR_CURRENT_VAL));

        if ((valueChanged || isPlaceholderValue) && elem.getAttribute(ATTR_ACTIVE) === "true") {
            elem.removeAttribute(ATTR_ACTIVE);
            elem.value = elem.value.replace(elem.getAttribute(ATTR_CURRENT_VAL), "");
            elem.className = elem.className.replace(classNameRegExp, "");

            // Restore the maxlength value
            maxLength = elem.getAttribute(ATTR_MAXLENGTH);
            if (parseInt(maxLength, 10) >= 0) { // Old FF returns -1 if attribute not set (see GH-56)
                elem.setAttribute("maxLength", maxLength);
                elem.removeAttribute(ATTR_MAXLENGTH);
            }

            // If the polyfill has changed the type of the element we need to change it back
            type = elem.getAttribute(ATTR_INPUT_TYPE);
            if (type) {
                elem.type = type;
            }
            return true;
        }
        return false;
    }

    // Show the placeholder value on a single element. Returns true if the placeholder was shown and false if it was not (because it was already visible)
    function showPlaceholder(elem) {
        var type,
            maxLength,
            val = elem.getAttribute(ATTR_CURRENT_VAL);
        if (elem.value === "" && val) {
            elem.setAttribute(ATTR_ACTIVE, "true");
            elem.value = val;
            elem.className += " " + placeholderClassName;

            // Store and remove the maxlength value
            maxLength = elem.getAttribute(ATTR_MAXLENGTH);
            if (!maxLength) {
                elem.setAttribute(ATTR_MAXLENGTH, elem.maxLength);
                elem.removeAttribute("maxLength");
            }

            // If the type of element needs to change, change it (e.g. password inputs)
            type = elem.getAttribute(ATTR_INPUT_TYPE);
            if (type) {
                elem.type = "text";
            } else if (elem.type === "password") {
                if (Utils.changeType(elem, "text")) {
                    elem.setAttribute(ATTR_INPUT_TYPE, "password");
                }
            }
            return true;
        }
        return false;
    }

    function handleElem(node, callback) {

        var handleInputsLength, handleTextareasLength, handleInputs, handleTextareas, elem, len, i;

        // Check if the passed in node is an input/textarea (in which case it can't have any affected descendants)
        if (node && node.getAttribute(ATTR_CURRENT_VAL)) {
            callback(node);
        } else {

            // If an element was passed in, get all affected descendants. Otherwise, get all affected elements in document
            handleInputs = node ? node.getElementsByTagName("input") : inputs;
            handleTextareas = node ? node.getElementsByTagName("textarea") : textareas;

            handleInputsLength = handleInputs ? handleInputs.length : 0;
            handleTextareasLength = handleTextareas ? handleTextareas.length : 0;

            // Run the callback for each element
            for (i = 0, len = handleInputsLength + handleTextareasLength; i < len; i++) {
                elem = i < handleInputsLength ? handleInputs[i] : handleTextareas[i - handleInputsLength];
                callback(elem);
            }
        }
    }

    // Return all affected elements to their normal state (remove placeholder value if present)
    function disablePlaceholders(node) {
        handleElem(node, hidePlaceholder);
    }

    // Show the placeholder value on all appropriate elements
    function enablePlaceholders(node) {
        handleElem(node, showPlaceholder);
    }

    // Returns a function that is used as a focus event handler
    function makeFocusHandler(elem) {
        return function () {

            // Only hide the placeholder value if the (default) hide-on-focus behaviour is enabled
            if (hideOnInput && elem.value === elem.getAttribute(ATTR_CURRENT_VAL) && elem.getAttribute(ATTR_ACTIVE) === "true") {

                // Move the caret to the start of the input (this mimics the behaviour of all browsers that do not hide the placeholder on focus)
                Utils.moveCaret(elem, 0);

            } else {

                // Remove the placeholder
                hidePlaceholder(elem);
            }
        };
    }

    // Returns a function that is used as a blur event handler
    function makeBlurHandler(elem) {
        return function () {
            showPlaceholder(elem);
        };
    }

    // Functions that are used as a event handlers when the hide-on-input behaviour has been activated - very basic implementation of the "input" event
    function makeKeydownHandler(elem) {
        return function (e) {
            keydownVal = elem.value;

            //Prevent the use of the arrow keys (try to keep the cursor before the placeholder)
            if (elem.getAttribute(ATTR_ACTIVE) === "true") {
                if (keydownVal === elem.getAttribute(ATTR_CURRENT_VAL) && Utils.inArray(badKeys, e.keyCode)) {
                    if (e.preventDefault) {
                        e.preventDefault();
                    }
                    return false;
                }
            }
        };
    }
    function makeKeyupHandler(elem) {
        return function () {
            hidePlaceholder(elem, keydownVal);

            // If the element is now empty we need to show the placeholder
            if (elem.value === "") {
                elem.blur();
                Utils.moveCaret(elem, 0);
            }
        };
    }
    function makeClickHandler(elem) {
        return function () {
            if (elem === safeActiveElement() && elem.value === elem.getAttribute(ATTR_CURRENT_VAL) && elem.getAttribute(ATTR_ACTIVE) === "true") {
                Utils.moveCaret(elem, 0);
            }
        };
    }

    // Returns a function that is used as a submit event handler on form elements that have children affected by this polyfill
    function makeSubmitHandler(form) {
        return function () {

            // Turn off placeholders on all appropriate descendant elements
            disablePlaceholders(form);
        };
    }

    // Bind event handlers to an element that we need to affect with the polyfill
    function newElement(elem) {

        // If the element is part of a form, make sure the placeholder string is not submitted as a value
        if (elem.form) {
            form = elem.form;

            // If the type of the property is a string then we have a "form" attribute and need to get the real form
            if (typeof form === "string") {
                form = document.getElementById(form);
            }

            // Set a flag on the form so we know it's been handled (forms can contain multiple inputs)
            if (!form.getAttribute(ATTR_FORM_HANDLED)) {
                Utils.addEventListener(form, "submit", makeSubmitHandler(form));
                form.setAttribute(ATTR_FORM_HANDLED, "true");
            }
        }

        // Bind event handlers to the element so we can hide/show the placeholder as appropriate
        Utils.addEventListener(elem, "focus", makeFocusHandler(elem));
        Utils.addEventListener(elem, "blur", makeBlurHandler(elem));

        // If the placeholder should hide on input rather than on focus we need additional event handlers
        if (hideOnInput) {
            Utils.addEventListener(elem, "keydown", makeKeydownHandler(elem));
            Utils.addEventListener(elem, "keyup", makeKeyupHandler(elem));
            Utils.addEventListener(elem, "click", makeClickHandler(elem));
        }

        // Remember that we've bound event handlers to this element
        elem.setAttribute(ATTR_EVENTS_BOUND, "true");
        elem.setAttribute(ATTR_CURRENT_VAL, placeholder);

        // If the element doesn't have a value and is not focussed, set it to the placeholder string
        if (hideOnInput || elem !== safeActiveElement()) {
            showPlaceholder(elem);
        }
    }

    Placeholders.nativeSupport = test.placeholder !== void 0;

    if (!Placeholders.nativeSupport) {

        // Get references to all the input and textarea elements currently in the DOM (live NodeList objects to we only need to do this once)
        inputs = document.getElementsByTagName("input");
        textareas = document.getElementsByTagName("textarea");

        // Get any settings declared as data-* attributes on the root element (currently the only options are whether to hide the placeholder on focus or input and whether to auto-update)
        hideOnInput = root.getAttribute(ATTR_OPTION_FOCUS) === "false";
        liveUpdates = root.getAttribute(ATTR_OPTION_LIVE) !== "false";

        // Create style element for placeholder styles (instead of directly setting style properties on elements - allows for better flexibility alongside user-defined styles)
        styleElem = document.createElement("style");
        styleElem.type = "text/css";

        // Create style rules as text node
        styleRules = document.createTextNode("." + placeholderClassName + " { color:" + placeholderStyleColor + "; }");

        // Append style rules to newly created stylesheet
        if (styleElem.styleSheet) {
            styleElem.styleSheet.cssText = styleRules.nodeValue;
        } else {
            styleElem.appendChild(styleRules);
        }

        // Prepend new style element to the head (before any existing stylesheets, so user-defined rules take precedence)
        head.insertBefore(styleElem, head.firstChild);

        // Set up the placeholders
        for (i = 0, len = inputs.length + textareas.length; i < len; i++) {
            elem = i < inputs.length ? inputs[i] : textareas[i - inputs.length];

            // Get the value of the placeholder attribute, if any. IE10 emulating IE7 fails with getAttribute, hence the use of the attributes node
            placeholder = elem.attributes.placeholder;
            if (placeholder) {

                // IE returns an empty object instead of undefined if the attribute is not present
                placeholder = placeholder.nodeValue;

                // Only apply the polyfill if this element is of a type that supports placeholders, and has a placeholder attribute with a non-empty value
                if (placeholder && Utils.inArray(validTypes, elem.type)) {
                    newElement(elem);
                }
            }
        }

        // If enabled, the polyfill will repeatedly check for changed/added elements and apply to those as well
        timer = setInterval(function () {
            for (i = 0, len = inputs.length + textareas.length; i < len; i++) {
                elem = i < inputs.length ? inputs[i] : textareas[i - inputs.length];

                // Only apply the polyfill if this element is of a type that supports placeholders, and has a placeholder attribute with a non-empty value
                placeholder = elem.attributes.placeholder;
                if (placeholder) {
                    placeholder = placeholder.nodeValue;
                    if (placeholder && Utils.inArray(validTypes, elem.type)) {

                        // If the element hasn't had event handlers bound to it then add them
                        if (!elem.getAttribute(ATTR_EVENTS_BOUND)) {
                            newElement(elem);
                        }

                        // If the placeholder value has changed or not been initialised yet we need to update the display
                        if (placeholder !== elem.getAttribute(ATTR_CURRENT_VAL) || (elem.type === "password" && !elem.getAttribute(ATTR_INPUT_TYPE))) {

                            // Attempt to change the type of password inputs (fails in IE < 9)
                            if (elem.type === "password" && !elem.getAttribute(ATTR_INPUT_TYPE) && Utils.changeType(elem, "text")) {
                                elem.setAttribute(ATTR_INPUT_TYPE, "password");
                            }

                            // If the placeholder value has changed and the placeholder is currently on display we need to change it
                            if (elem.value === elem.getAttribute(ATTR_CURRENT_VAL)) {
                                elem.value = placeholder;
                            }

                            // Keep a reference to the current placeholder value in case it changes via another script
                            elem.setAttribute(ATTR_CURRENT_VAL, placeholder);
                        }
                    }
                } else if (elem.getAttribute(ATTR_ACTIVE)) {
                    hidePlaceholder(elem);
                    elem.removeAttribute(ATTR_CURRENT_VAL);
                }
            }

            // If live updates are not enabled cancel the timer
            if (!liveUpdates) {
                clearInterval(timer);
            }
        }, 100);
    }

    Utils.addEventListener(global, "beforeunload", function () {
        Placeholders.disable();
    });

    // Expose public methods
    Placeholders.disable = Placeholders.nativeSupport ? noop : disablePlaceholders;
    Placeholders.enable = Placeholders.nativeSupport ? noop : enablePlaceholders;

}(this));