图片懒加载

缺乏、安全感 2022-06-16 06:44 485阅读 0赞

1.引入js jquery.lazyload.js(如下)

/*
     * Lazy Load - jQuery plugin for lazy loading images
     *
     * Copyright (c) 2007-2009 Mika Tuupola
     *
     * Licensed under the MIT license:
     *   http://www.opensource.org/licenses/mit-license.php
     *
     * Project home:
     *   http://www.appelsiini.net/projects/lazyload
     *
     * Version:  1.5.0
     *
     */
    (function($) {
    
        $.fn.lazyload = function(options) {
            var settings = {
                threshold    : 0,
                failurelimit : 0,
                event        : "scroll",
                effect       : "show",
                container    : window
            };
                    
            if(options) {
                $.extend(settings, options);
            }
    
            /* Fire one scroll event per scroll. Not one scroll event per image. */
            var elements = this;
            if ("scroll" == settings.event) {
                $(settings.container).bind("scroll", function(event) {
                    
                    var counter = 0;
                    elements.each(function() {
                        if ($.abovethetop(this, settings) ||
                            $.leftofbegin(this, settings)) {
                                /* Nothing. */
                        } else if (!$.belowthefold(this, settings) &&
                            !$.rightoffold(this, settings)) {
                                $(this).trigger("appear");
                        } else {
                            if (counter++ > settings.failurelimit) {
                                return false;
                            }
                        }
                    });
                    /* Remove image from array so it is not looped next time. */
                    var temp = $.grep(elements, function(element) {
                        return !element.loaded;
                    });
                    elements = $(temp);
                });
            }
            
            this.each(function() {
                var self = this;
    				/* Save original only if it is not defined in HTML. */
    				if (undefined == $(self).attr("original")) {
    					$(self).attr("original", $(self).attr("src"));
    				}
    
                if ("scroll" != settings.event || 
                        undefined == $(self).attr("src") || 
                        settings.placeholder == $(self).attr("src") || 
                        ($.abovethetop(self, settings) ||
                         $.leftofbegin(self, settings) || 
                         $.belowthefold(self, settings) || 
                         $.rightoffold(self, settings) )) {
                            
                    if (settings.placeholder) {
                        $(self).attr("src", settings.placeholder);      
                    } else {
                        $(self).removeAttr("src");
                    }
                    self.loaded = false;
                } else {
                    self.loaded = true;
                }
                
                /* When appear is triggered load original image. */
                $(self).one("appear", function() {
                    if (!this.loaded) {
                        $("<img />")
                            .bind("load", function() {
                                $(self)
                                    .hide()
                                    .attr("src", $(self).attr("original"))
                                    [settings.effect](settings.effectspeed);
                                self.loaded = true;
                            })
                            .attr("src", $(self).attr("original"));
                    };
                });
    
                /* When wanted event is triggered load original image */
                /* by triggering appear.                              */
                if ("scroll" != settings.event) {
                    $(self).bind(settings.event, function(event) {
                        if (!self.loaded) {
                            $(self).trigger("appear");
                        }
                    });
                }
            });
            
            /* Force initial check if images should appear. */
            $(settings.container).trigger(settings.event);
            
            return this;
    
        };
    
        /* Convenience methods in jQuery namespace.           */
        /* Use as  $.belowthefold(element, {threshold : 100, container : window}) */
    
        $.belowthefold = function(element, settings) {
            if (settings.container === undefined || settings.container === window) {
                var fold = $(window).height() + $(window).scrollTop();
            } else {
                var fold = $(settings.container).offset().top + $(settings.container).height();
            }
            return fold <= $(element).offset().top - settings.threshold;
        };
        
        $.rightoffold = function(element, settings) {
            if (settings.container === undefined || settings.container === window) {
                var fold = $(window).width() + $(window).scrollLeft();
            } else {
                var fold = $(settings.container).offset().left + $(settings.container).width();
            }
            return fold <= $(element).offset().left - settings.threshold;
        };
            
        $.abovethetop = function(element, settings) {
            if (settings.container === undefined || settings.container === window) {
                var fold = $(window).scrollTop();
            } else {
                var fold = $(settings.container).offset().top;
            }
            return fold >= $(element).offset().top + settings.threshold  + $(element).height();
        };
        
        $.leftofbegin = function(element, settings) {
            if (settings.container === undefined || settings.container === window) {
                var fold = $(window).scrollLeft();
            } else {
                var fold = $(settings.container).offset().left;
            }
            return fold >= $(element).offset().left + settings.threshold + $(element).width();
        };
        /* Custom selectors for your convenience.   */
        /* Use as $("img:below-the-fold").something() */
    
        $.extend($.expr[':'], {
            "below-the-fold" : "$.belowthefold(a, {threshold : 0, container: window})",
            "above-the-fold" : "!$.belowthefold(a, {threshold : 0, container: window})",
            "right-of-fold"  : "$.rightoffold(a, {threshold : 0, container: window})",
            "left-of-fold"   : "!$.rightoffold(a, {threshold : 0, container: window})"
        });
        
    })(jQuery);

2.初始化页面

$(function(){
    	$(".body_main img").lazyload({
            effect : "fadeIn",
            failurelimit : 5
    
        });
    });

![Center][]

![Center 1][]

[Center]: /images/20220616/91d14ef1daaf4147b30d973012800035.png
[Center 1]: /images/20220616/bd6b4858e7a74c8fb051d51205a29668.png