占位符不适用于Internet Explorer

Question

以下格式的文本框占位符不适用于Internet Explorer.无论如何在Internet Explorer中显示TextBox的占位符？

<asp:TextBox id="email" runat="server" width="300" placeholder="Your email" />

有没有简单的方法只使用任何JavaScript.我不想使用jQuery使它变得复杂.

Answer 1

你可以使用纯JavaScript模仿这个:

var _debug = false;
var _placeholderSupport = function() {
    var t = document.createElement("input");
    t.type = "text";
    return (typeof t.placeholder !== "undefined");
}();

window.onload = function() {
    var arrInputs = document.getElementsByTagName("input");
    var arrTextareas = document.getElementsByTagName("textarea");
    var combinedArray = [];
    for (var i = 0; i < arrInputs.length; i++)
        combinedArray.push(arrInputs[i]);
    for (var i = 0; i < arrTextareas.length; i++)
        combinedArray.push(arrTextareas[i]);
    for (var i = 0; i < combinedArray.length; i++) {
        var curInput = combinedArray[i];
        if (!curInput.type || curInput.type == "" || curInput.type == "text" || curInput.type == "textarea")
            HandlePlaceholder(curInput);
        else if (curInput.type == "password")
            ReplaceWithText(curInput);
    }

    if (!_placeholderSupport) {
        for (var i = 0; i < document.forms.length; i++) {
            var oForm = document.forms[i];
            if (oForm.attachEvent) {
                oForm.attachEvent("onsubmit", function() {
                    PlaceholderFormSubmit(oForm);
                });
            }
            else if (oForm.addEventListener)
                oForm.addEventListener("submit", function() {
                    PlaceholderFormSubmit(oForm);
                }, false);
        }
    }
};

function PlaceholderFormSubmit(oForm) {    
    for (var i = 0; i < oForm.elements.length; i++) {
        var curElement = oForm.elements[i];
        HandlePlaceholderItemSubmit(curElement);
    }
}

function HandlePlaceholderItemSubmit(element) {
    if (element.name) {
        var curPlaceholder = element.getAttribute("placeholder");
        if (curPlaceholder && curPlaceholder.length > 0 && element.value === curPlaceholder) {
            element.value = "";
            window.setTimeout(function() {
                element.value = curPlaceholder;
            }, 100);
        }
    }
}

function ReplaceWithText(oPasswordTextbox) {
    if (_placeholderSupport)
        return;
    var oTextbox = document.createElement("input");
    oTextbox.type = "text";
    oTextbox.id = oPasswordTextbox.id;
    oTextbox.name = oPasswordTextbox.name;
    //oTextbox.style = oPasswordTextbox.style;
    oTextbox.className = oPasswordTextbox.className;
    for (var i = 0; i < oPasswordTextbox.attributes.length; i++) {
        var curName = oPasswordTextbox.attributes.item(i).nodeName;
        var curValue = oPasswordTextbox.attributes.item(i).nodeValue;
        if (curName !== "type" && curName !== "name") {
            oTextbox.setAttribute(curName, curValue);
        }
    }
    oTextbox.originalTextbox = oPasswordTextbox;
    oPasswordTextbox.parentNode.replaceChild(oTextbox, oPasswordTextbox);
    HandlePlaceholder(oTextbox);
    if (!_placeholderSupport) {
        oPasswordTextbox.onblur = function() {
            if (this.dummyTextbox && this.value.length === 0) {
                this.parentNode.replaceChild(this.dummyTextbox, this);
            }
        };
    }
}

function HandlePlaceholder(oTextbox) {
    if (!_placeholderSupport) {
        var curPlaceholder = oTextbox.getAttribute("placeholder");
        if (curPlaceholder && curPlaceholder.length > 0) {
            Debug("Placeholder found for input box '" + oTextbox.name + "': " + curPlaceholder);
            oTextbox.value = curPlaceholder;
            oTextbox.setAttribute("old_color", oTextbox.style.color);
            oTextbox.style.color = "#c0c0c0";
            oTextbox.onfocus = function() {
                var _this = this;
                if (this.originalTextbox) {
                    _this = this.originalTextbox;
                    _this.dummyTextbox = this;
                    this.parentNode.replaceChild(this.originalTextbox, this);
                    _this.focus();
                }
                Debug("input box '" + _this.name + "' focus");
                _this.style.color = _this.getAttribute("old_color");
                if (_this.value === curPlaceholder)
                    _this.value = "";
            };
            oTextbox.onblur = function() {
                var _this = this;
                Debug("input box '" + _this.name + "' blur");
                if (_this.value === "") {
                    _this.style.color = "#c0c0c0";
                    _this.value = curPlaceholder;
                }
            };
        }
        else {
            Debug("input box '" + oTextbox.name + "' does not have placeholder attribute");
        }
    }
    else {
        Debug("browser has native support for placeholder");
    }
}

function Debug(msg) {
    if (typeof _debug !== "undefined" && _debug) {
        var oConsole = document.getElementById("Console");
        if (!oConsole) {
            oConsole = document.createElement("div");
            oConsole.id = "Console";
            document.body.appendChild(oConsole);
        }
        oConsole.innerHTML += msg + "<br />";
    }
}

如果浏览器已经支持该placeholder属性,这将不起作用,并且如果它不受支持(例如浏览器是IE),它将添加非常类似的功能 - 默认显示的文本在焦点上消失并且如果用户没有键入则再次出现任何东西.

现场测试案例.

Bug修复

2012年11月6日:以前的代码无法检测浏览器何时没有占位符的原生支持.使用在另一篇文章中找到的代码现在已修复.受影响的浏览器:IE7和IE8,也许还有其他浏览器.还添加了调试支持以帮助调试未来的问题.

2013年1月30日:

1. 添加对密码输入的支持.由于IE8及以下版本不允许动态更改输入类型,只要没有输入密码,代码就会用文本输入替换密码输入,因此占位符文本将可见.

2. 修复了在提交与输入关联的表单时发送占位符值的错误,其中应将空值发送到服务器.为此,代码将附加到表单提交事件,并在需要时清除值.

2014年1月24日:添加对<textarea>元素的支持.