chooks/utils/easing.js

基于 [`@vue/composition-api`](https://github.com/vuejs/composition-api) 的vue hooks函数

let pow = Math.pow,
    sqrt = Math.sqrt,
    sin = Math.sin,
    cos = Math.cos,
    PI = Math.PI,
    c1 = 1.70158,
    c2 = c1 * 1.525,
    c3 = c1 + 1,
    c4 = (2 * PI) / 3,
    c5 = (2 * PI) / 4.5;

function bounceOut(x) {
	var n1 = 7.5625,
		d1 = 2.75;
	if ( x < 1/d1 ) {
		return n1*x*x;
	} else if ( x < 2/d1 ) {
		return n1*(x-=(1.5/d1))*x + .75;
	} else if ( x < 2.5/d1 ) {
		return n1*(x-=(2.25/d1))*x + .9375;
	} else {
		return n1*(x-=(2.625/d1))*x + .984375;
	}
}

export default {
    easeInQuad: function(x) {
        return x * x;
    },
    easeOutQuad: function(x) {
        return 1 - (1 - x) * (1 - x);
    },
    easeInOutQuad: function(x) {
        return x < 0.5 ?
            2 * x * x :
            1 - pow(-2 * x + 2, 2) / 2;
    },
    easeInCubic: function(x) {
        return x * x * x;
    },
    easeOutCubic: function(x) {
        return 1 - pow(1 - x, 3);
    },
    easeInOutCubic: function(x) {
        return x < 0.5 ?
            4 * x * x * x :
            1 - pow(-2 * x + 2, 3) / 2;
    },
    easeInQuart: function(x) {
        return x * x * x * x;
    },
    easeOutQuart: function(x) {
        return 1 - pow(1 - x, 4);
    },
    easeInOutQuart: function(x) {
        return x < 0.5 ?
            8 * x * x * x * x :
            1 - pow(-2 * x + 2, 4) / 2;
    },
    easeInQuint: function(x) {
        return x * x * x * x * x;
    },
    easeOutQuint: function(x) {
        return 1 - pow(1 - x, 5);
    },
    easeInOutQuint: function(x) {
        return x < 0.5 ?
            16 * x * x * x * x * x :
            1 - pow(-2 * x + 2, 5) / 2;
    },
    easeInSine: function(x) {
        return 1 - cos(x * PI / 2);
    },
    easeOutSine: function(x) {
        return sin(x * PI / 2);
    },
    easeInOutSine: function(x) {
        return -(cos(PI * x) - 1) / 2;
    },
    easeInExpo: function(x) {
        return x === 0 ? 0 : pow(2, 10 * x - 10);
    },
    easeOutExpo: function(x) {
        return x === 1 ? 1 : 1 - pow(2, -10 * x);
    },
    easeInOutExpo: function(x) {
        return x === 0 ? 0 : x === 1 ? 1 : x < 0.5 ?
            pow(2, 20 * x - 10) / 2 :
            (2 - pow(2, -20 * x + 10)) / 2;
    },
    easeInCirc: function(x) {
        return 1 - sqrt(1 - pow(x, 2));
    },
    easeOutCirc: function(x) {
        return sqrt(1 - pow(x - 1, 2));
    },
    easeInOutCirc: function(x) {
        return x < 0.5 ?
            (1 - sqrt(1 - pow(2 * x, 2))) / 2 :
            (sqrt(1 - pow(-2 * x + 2, 2)) + 1) / 2;
    },
    easeInElastic: function(x) {
        return x === 0 ? 0 : x === 1 ? 1 :
            -pow(2, 10 * x - 10) * sin((x * 10 - 10.75) * c4);
    },
    easeOutElastic: function(x) {
        return x === 0 ? 0 : x === 1 ? 1 :
            pow(2, -10 * x) * sin((x * 10 - 0.75) * c4) + 1;
    },
    easeInOutElastic: function(x) {
        return x === 0 ? 0 : x === 1 ? 1 : x < 0.5 ?
            -(pow(2, 20 * x - 10) * sin((20 * x - 11.125) * c5)) / 2 :
            pow(2, -20 * x + 10) * sin((20 * x - 11.125) * c5) / 2 + 1;
    },
    easeInBack: function(x) {
        return c3 * x * x * x - c1 * x * x;
    },
    easeOutBack: function(x) {
        return 1 + c3 * pow(x - 1, 3) + c1 * pow(x - 1, 2);
    },
    easeInOutBack: function(x) {
        return x < 0.5 ?
            (pow(2 * x, 2) * ((c2 + 1) * 2 * x - c2)) / 2 :
            (pow(2 * x - 2, 2) * ((c2 + 1) * (x * 2 - 2) + c2) + 2) / 2;
    },
    easeInBounce: function(x) {
        return 1 - bounceOut(1 - x);
    },
    easeOutBounce: bounceOut,
    easeInOutBounce: function(x) {
        return x < 0.5 ?
            (1 - bounceOut(1 - 2 * x)) / 2 :
            (1 + bounceOut(2 * x - 1)) / 2;
    }
}