實現加入購物車效果
前言加入購物車功能，在商城類移動端或 app 上經常出現。增加了體驗，在此基礎上自己封裝一個來實現。
1.原理
點擊商品顯示一個小球，從商品出發到達數量 box，且小球得大小逐漸變小。
2.如何實現拋物運動
- 1.認識 tween 函數
- 2.tween與小球的位置關係
- 3.獲取小球起始點方法
- 4.定時器函數更新小球位置
2.1 tween 函數
tween 主要是利用數學公式讓數值從某個值變爲某個值用線性關係表示出來，如(y=x)當然不僅僅如此簡單，主要得有
Linear ==> 線性勻速運動效果
Quadratic ==> 二次方的緩動（t^2）
Cubic ==> 三次方的緩動（）
Quartic ==> 四次方的緩動（）
Quintic ==> 五次方的緩動
Sinusoidal ==> 正弦曲線的緩動（）
Exponential ==> 指數曲線的緩動（）
Circular ==> 圓形曲線的緩動（）
Elastic ==> 指數衰減的正弦曲線緩動（）
Back ==> 超過範圍的三次方的緩動
Bounce ==> 指數衰減的反彈緩動
//t 起始時間固定爲0 d 持續時間默認300 b起始值 c變化量(如 0-> 100=(100-0=100),1->0=(0-1=-1))
let Tween = {
Linear: function (t, b, c, d) {
return c * t / d + b;
},
Quad: {
easeIn: function (t, b, c, d) {
return c * (t /= d) * t + b;
},
easeOut: function (t, b, c, d) {
return -c * (t /= d) * (t - 2) + b;
},
easeInOut: function (t, b, c, d) {
if ((t /= d / 2) < 1) return c / 2 * t * t + b;
return -c / 2 * ((--t) * (t - 2) - 1) + b;
}
},
Cubic: {
easeIn: function (t, b, c, d) {
return c * (t /= d) * t * t + b;
},
easeOut: function (t, b, c, d) {
return c * ((t = t / d - 1) * t * t + 1) + b;
},
easeInOut: function (t, b, c, d) {
if ((t /= d / 2) < 1) return c / 2 * t * t * t + b;
return c / 2 * ((t -= 2) * t * t + 2) + b;
}
},
Quart: {
easeIn: function (t, b, c, d) {
return c * (t /= d) * t * t * t + b;
},
easeOut: function (t, b, c, d) {
return -c * ((t = t / d - 1) * t * t * t - 1) + b;
},
easeInOut: function (t, b, c, d) {
if ((t /= d / 2) < 1) return c / 2 * t * t * t * t + b;
return -c / 2 * ((t -= 2) * t * t * t - 2) + b;
}
},
Quint: {
easeIn: function (t, b, c, d) {
return c * (t /= d) * t * t * t * t + b;
},
easeOut: function (t, b, c, d) {
return c * ((t = t / d - 1) * t * t * t * t + 1) + b;
},
easeInOut: function (t, b, c, d) {
if ((t /= d / 2) < 1) return c / 2 * t * t * t * t * t + b;
return c / 2 * ((t -= 2) * t * t * t * t + 2) + b;
}
},
Sine: {
easeIn: function (t, b, c, d) {
return -c * Math.cos(t / d * (Math.PI / 2)) + c + b;
},
easeOut: function (t, b, c, d) {
return c * Math.sin(t / d * (Math.PI / 2)) + b;
},
easeInOut: function (t, b, c, d) {
return -c / 2 * (Math.cos(Math.PI * t / d) - 1) + b;
}
},
Expo: {
easeIn: function (t, b, c, d) {
return (t == 0) ? b : c * Math.pow(2, 10 * (t / d - 1)) + b;
},
easeOut: function (t, b, c, d) {
return (t == d) ? b + c : c * (-Math.pow(2, -10 * t / d) + 1) + b;
},
easeInOut: function (t, b, c, d) {
if (t == 0) return b;
if (t == d) return b + c;
if ((t /= d / 2) < 1) return c / 2 * Math.pow(2, 10 * (t - 1)) + b;
return c / 2 * (-Math.pow(2, -10 * --t) + 2) + b;
}
},
Circ: {
easeIn: function (t, b, c, d) {
return -c * (Math.sqrt(1 - (t /= d) * t) - 1) + b;
},
easeOut: function (t, b, c, d) {
return c * Math.sqrt(1 - (t = t / d - 1) * t) + b;
},
easeInOut: function (t, b, c, d) {
if ((t /= d / 2) < 1) return -c / 2 * (Math.sqrt(1 - t * t) - 1) + b;
return c / 2 * (Math.sqrt(1 - (t -= 2) * t) + 1) + b;
}
},
Elastic: {
easeIn: function (t, b, c, d, a, p) {
var s;
if (t == 0) return b;
if ((t /= d) == 1) return b + c;
if (typeof p == "undefined") p = d * .3;
if (!a || a < Math.abs(c)) {
s = p / 4;
a = c;
} else {
s = p / (2 * Math.PI) * Math.asin(c / a);
}
return -(a * Math.pow(2, 10 * (t -= 1)) * Math.sin((t * d - s) * (2 * Math.PI) / p)) + b;
},
easeOut: function (t, b, c, d, a, p) {
var s;
if (t == 0) return b;
if ((t /= d) == 1) return b + c;
if (typeof p == "undefined") p = d * .3;
if (!a || a < Math.abs(c)) {
a = c;
s = p / 4;
} else {
s = p / (2 * Math.PI) * Math.asin(c / a);
}
return (a * Math.pow(2, -10 * t) * Math.sin((t * d - s) * (2 * Math.PI) / p) + c + b);
},
easeInOut: function (t, b, c, d, a, p) {
var s;
if (t == 0) return b;
if ((t /= d / 2) == 2) return b + c;
if (typeof p == "undefined") p = d * (.3 * 1.5);
if (!a || a < Math.abs(c)) {
a = c;
s = p / 4;
} else {
s = p / (2 * Math.PI) * Math.asin(c / a);
}
if (t < 1) return -.5 * (a * Math.pow(2, 10 * (t -= 1)) * Math.sin((t * d - s) * (2 * Math.PI) / p)) + b;
return a * Math.pow(2, -10 * (t -= 1)) * Math.sin((t * d - s) * (2 * Math.PI) / p) * .5 + c + b;
}
},
Back: {
easeIn: function (t, b, c, d, s) {
if (typeof s == "undefined") s = 1.70158;
return c * (t /= d) * t * ((s + 1) * t - s) + b;
},
easeOut: function (t, b, c, d, s) {
if (typeof s == "undefined") s = 1.70158;
return c * ((t = t / d - 1) * t * ((s + 1) * t + s) + 1) + b;
},
easeInOut: function (t, b, c, d, s) {
if (typeof s == "undefined") s = 1.70158;
if ((t /= d / 2) < 1) return c / 2 * (t * t * (((s *= (1.525)) + 1) * t - s)) + b;
return c / 2 * ((t -= 2) * t * (((s *= (1.525)) + 1) * t + s) + 2) + b;
}
},
Bounce: {
easeIn: function (t, b, c, d) {
return c - Tween.Bounce.easeOut(d - t, 0, c, d) + b;
},
easeOut: function (t, b, c, d) {
if ((t /= d) < (1 / 2.75)) {
return c * (7.5625 * t * t) + b;
} else if (t < (2 / 2.75)) {
return c * (7.5625 * (t -= (1.5 / 2.75)) * t + .75) + b;
} else if (t < (2.5 / 2.75)) {
return c * (7.5625 * (t -= (2.25 / 2.75)) * t + .9375) + b;
} else {
return c * (7.5625 * (t -= (2.625 / 2.75)) * t + .984375) + b;
}
},
easeInOut: function (t, b, c, d) {
if (t < d / 2) {
return Tween.Bounce.easeIn(t * 2, 0, c, d) * .5 + b;
} else {
return Tween.Bounce.easeOut(t * 2 - d, 0, c, d) * .5 + c * .5 + b;
}
}
}
}
當然這裏有更主要得解釋: 關於 tween 函數
2.2tween 函數與小球關係
我們只需要關注小球得起始點和末尾點，至於小球位置以何種線性變化完全可以交給 tween 函數。
2.3 如何獲取小球得起始位置
可以利用 dom.offsetLeft 獲取，但 getBoundClientRect()兼容性比它更好，更推薦使用該函數獲取其距離視口的寬高。
getBoundPos(obj = null) {
return obj.getBoundingClientRect();
}
2.4定時器函數更新小球位置
定時器函數在指定時間內執行tween函數返回值，來設置當前小球位置
let valueX = Tween[effect].easeOut(loopCount, startX, changedX, duration);
let valueY = Tween[effect].easeIn(loopCount, startY, changedY, duration);
let scalRate = Tween[effect].easeIn(loopCount,1,-1,duration);
dom.style.left = valueX + 'px';
dom.style.top = valueY + 'px';
dom.style.transform = `scale(${scalRate})`
3.完整的實現方法
class Fly {
constructor(params = {}) {
this.options = {
dom: null, //飛翔得小球
origin: null, //起點位置
target: null, //終點
effect: 'Quad',
duration: 30, //循環時間
onUpdate() { }, //更新中得回調
onComplete() { },
...params
};
this.startX = this.getBoundPos(this.options.origin).left;
this.startY = this.getBoundPos(this.options.origin).top;
this.endX = this.getBoundPos(this.options.target).left;
this.endY = this.getBoundPos(this.options.target).top;
this.changedX = this.endX - this.startX;
this.changedY = this.endY - this.startY;
this.loopCount = 0; //起始時間
this.interval = null;
}
init() {
this.interval = setInterval(() => {
this.updateTimer()
}, 1000 / 60)
}
updateTimer() {
let {
options: {
dom,
effect,
duration,
onUpdate,
onComplete
},
loopCount,
startX,
startY,
changedX,
changedY } = this;
this.loopCount++
let valueX = Tween[effect].easeOut(loopCount, startX, changedX, duration);
let valueY = Tween[effect].easeIn(loopCount, startY, changedY, duration);
let scalRate = Tween[effect].easeIn(loopCount,1,-1,duration);
dom.style.left = valueX + 'px';
dom.style.top = valueY + 'px';
dom.style.transform = `scale(${scalRate})`
if (this.loopCount <= duration) {
onUpdate()
} else {
onComplete();
clearInterval(this.interval)
}
}
getBoundPos(obj = null) {
return obj.getBoundingClientRect();
}
}