在jQuery动画中向前跳? [英] jump forward in jQuery animation?

问题描述

有没有办法使jQuery动画在时间上向前/向后跳转?

Is there a way to jump a jQuery animation forward / backward in time?

例如，如果我在一个元素上设置了一个动画要花费10秒，我可以跳到该动画中的"5秒"吗?最好将其设置为百分比.

For example, if I have set an animation on an element to take 10 seconds, can I jump to '5 seconds' into that animation? Preferably, this could be set with a percentage.

推荐答案

除了百分比功能，它应该具有您想要的所有内容:

This should have everything you want but the percentage functionality:

演示: http://jsfiddle.net/SO_AMK/MHV5k/

jQuery:

var time = 10000; // Animation speed in ms
var opacity = 0; // Final desired opacity


function jumpAnimate(setOpacityTo, newOpacity, speed){  // I created a function to simplify things
    $("#fade").css("opacity", setOpacityTo).animate({
        "opacity": newOpacity
    }, {
        duration: speed // I used speed instead of time because time is already a global variable
    });
}

$("#jump").click(function(){
    var goTo = $("#jump-to").val(); // Get value from the text input

    var setOpacity = (1 / time) * (time - goTo); /* The opacity that the element should be set at, i.e. the actual jump
    Math is as follows: initial opacity / the speed of the original animation in ms * the time minus the desired animation stop in ms (basically the remaining time past the desired point) */

    $("#fade").stop(); // Stop the original animation after the math is finished so that we have minimal delay

    jumpAnimate(setOpacity, opacity, time - goTo); // Start a new animation
});

jumpAnimate(1, opacity, time);​ // Start the initial animation

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