discounts-minapp/utils/tool.js

//防抖debounce代码：
export function debounce(fn,delay=500) {
  var timeout = null; // 创建一个标记用来存放定时器的返回值
  return function (e) {
      // 每当用户输入的时候把前一个 setTimeout clear 掉
      clearTimeout(timeout); 
      // 然后又创建一个新的 setTimeout, 这样就能保证interval 间隔内如果时间持续触发，就不会执行 fn 函数
      timeout = setTimeout(() => {
          fn.apply(this, arguments);
      }, delay);
  };
}

// 返回两个经纬度之间的距离 单位米
const earthDistance = function (location1, location2) {
	    const lat1 = parseFloat(location1.lat);
	    const lng1 = parseFloat(location1.lng);
	    const lat2 = parseFloat(location2.lat);
	    const lng2 = parseFloat(location2.lng);
	
	    const EARTH_RADIUS = 6378137.0; //单位M
	    const PI = Math.PI;
	
	    function getRad(d) {
	        return d * PI / 180.0;
	    }
	
	    let f = getRad((lat1 + lat2) / 2);
	    let g = getRad((lat1 - lat2) / 2);
	    let l = getRad((lng1 - lng2) / 2);
	
	    let sg = Math.sin(g);
	    let sl = Math.sin(l);
	    let sf = Math.sin(f);
	
	    let s, c, w, r, d, h1, h2;
	    let a = EARTH_RADIUS;
	    let fl = 1 / 298.257;
	
	    sg = sg * sg;
	    sl = sl * sl;
	    sf = sf * sf;
	
	    s = sg * (1 - sl) + (1 - sf) * sl;
	    c = (1 - sg) * (1 - sl) + sf * sl;
	
	    w = Math.atan(Math.sqrt(s / c));
	    r = Math.sqrt(s * c) / w;
	    d = 2 * w * a;
	    h1 = (3 * r - 1) / 2 / c;
	    h2 = (3 * r + 1) / 2 / s;
	
	    return d * (1 + fl * (h1 * sf * (1 - sg) - h2 * (1 - sf) * sg));
	};


//rpx转换px  px=rpx * (屏幕宽度 / 750)
export const rpxTopx = function (rpx) {
			let width = uni.getWindowInfo().screenWidth
			let px = rpx *( width / 750 );
			return px
		}