How to get jQuery placeholder/watermark plugin to work for ajax loaded text fields?

Question

I'm using the following placeholder plugin

(function($){

    var ph = "PLACEHOLDER-INPUT";
    var phl = "PLACEHOLDER-LABEL";
    var boundEvents = false;
    var default_options = {
        labelClass: 'placeholder'
    };

    //check for native support for placeholder attribute, if so stub methods and return
    var input = document.createElement("input");
    if ('placeholder' in input) {
        $.fn.placeholder = $.fn.unplaceholder = function(){}; //empty function
        delete input; //cleanup IE memory
        return;
    };
    delete input;

    //bind to resize to fix placeholders when the page resizes (fields are hidden/displayed, which can change positioning).
    $(window).resize(checkResize);


    $.fn.placeholder = function(options) {
        bindEvents();

        var opts = $.extend(default_options, options)

        this.each(function(){
            var rnd=Math.random().toString(32).replace(/\./,'')
                ,input=$(this)
                ,label=$('<label style="position:absolute;display:none;top:0;left:0;"></label>');

            if (!input.attr('placeholder') || input.data(ph) === ph) return; //already watermarked

            //make sure the input tag has an ID assigned, if not, assign one.
            if (!input.attr('id')) input.attr('id', 'input_' + rnd);

            label   .attr('id',input.attr('id') + "_placeholder")
                    .data(ph, '#' + input.attr('id'))   //reference to the input tag
                    .attr('for',input.attr('id'))
                    .addClass(opts.labelClass)
                    .addClass(opts.labelClass + '-for-' + this.tagName.toLowerCase()) //ex: watermark-for-textarea
                    .addClass(phl)
                    .text(input.attr('placeholder'));

            input
                .data(phl, '#' + label.attr('id'))  //set a reference to the label
                .data(ph,ph)        //set that the field is watermarked
                .addClass(ph)       //add the watermark class
                .after(label)       //add the label field to the page

            //setup overlay
            itemFocus.call(this);
            itemBlur.call(this);
        });
    };

    $.fn.unplaceholder = function(){
        this.each(function(){
            var input=$(this),
                label=$(input.data(phl));

            if (input.data(ph) !== ph) return;

            label.remove();
            input.removeData(ph).removeData(phl).removeClass(ph).unbind('change',itemChange);
        });
    };

    function bindEvents() {
        if (boundEvents) return;

        //prepare live bindings if not already done.
        $("form").live('reset', function(){
            $(this).find('.' + ph).each(itemBlur);
        });
        $('.' + ph)
            .live('keydown',itemFocus)
            .live('mousedown',itemFocus)
            .live('mouseup',itemFocus)
            .live('mouseclick',itemFocus)
            .live('focus',itemFocus)
            .live('focusin',itemFocus)
            .live('blur',itemBlur)
            .live('focusout',itemBlur)
            .live('change',itemChange);
            ;
        $('.' + phl)
            .live('click', function() {  $($(this).data(ph)).focus(); })
            .live('mouseup', function() {  $($(this).data(ph)).focus(); });
        bound = true;

        boundEvents = true;
    };

    function itemChange() {
        var input = $(this);
        if (!!input.val()) {
            $(input.data(phl)).hide();
            return;
        }
        if (input.data(ph+'FOCUSED') != 1) {
            showPHL(input);
        }
    }

    function itemFocus() {
        $($(this).data(ph+'FOCUSED',1).data(phl)).hide();
    };

    function itemBlur() {
        var that = this;
        showPHL($(this).removeData(ph+'FOCUSED'));

        //use timeout to let other validators/formatters directly bound to blur/focusout work
        setTimeout(function(){
            var input = $(that);

            //if the item wasn't refocused, test the item
            if (input.data(ph+'FOCUSED') != 1) {
                showPHL(input);
            }
        }, 200);
    };

    function showPHL(input, forced) {
        var label = $(input.data(phl));

        //if not already shown, and needs to be, show it.
        if ((forced || label.css('display') == 'none') && !input.val())
            label
                .text(input.attr('placeholder'))
                .css('top', input.position().top + 'px')
                .css('left', input.position().left + 'px')
                .css('display', 'block');

        //console.dir({ 'input': { 'id':input.attr('id'), 'pos': input.position() }});
    }

    var cr;
    function checkResize() {
        if (cr) window.clearTimeout(cr);
        cr = window.setTimeout(checkResize2, 50);
    }
    function checkResize2() {
        $('.' + ph).each(function(){
            var input = $(this);
            var focused = $(this).data(ph+'FOCUSED');
            if (!focused) showPHL(input, true);
        });
    }

}(jQuery));  

It applies the placeholder attribute to form fields in browsers that do not natively support the placeholder attribute (ex. IE9). It works for statically loaded text fields, however for text fields that are loaded via ajax, the placeholder does not appear.

Is it possible to achieve this 'watermark' effect on text fields that are loaded via ajax?

Answer 1

You could apply the plugin to newly created controls after the AJAX call completes. Forgive the pseudo-code as I'm not really sure about how your AJAX calls are working:

$.ajax({
  url: "test.html",
  cache: false
}).done(function( result ) {
  field = $('<input>').html(result);
  $("#results").append(field);
  field.placeholder();
});

Another option is that you could use jQuery's .on() method to bind dynamically created controls to the function--but it wants an event (like click). I'm not sure how you would do that. Maybe something like this:

   $( 'body' ).on('click','input.addField', function(e){
        $(this).placeholder();
    });

I know this won't work, but maybe it helps get you brainstorm solutions.

Answer 2

如果在添加新输入后触发窗口调整大小功能会发生什么？

$(window).trigger('resize')