/**
 * 动态设置rem
 */

var BASE_SIZE = 20; // 基本字体大小
var MAX_SIZE = 50; // 最大字体大小
var DESIGN_WIDTH = 720; // iphone 6
var MIN_DESIGN_WIDTH = 320;
var htmlEl = document.querySelector('html');
var fontSize = 20;

var setFontSize = function (size) {
    htmlEl.style.fontSize = size + 'px';
    fontSize = size;
};

var calc = function () {
    var device_width = document.body.clientWidth || window.innerWidth;
    var scale = device_width / DESIGN_WIDTH;
    var distSize = scale * BASE_SIZE;
    if (distSize > MAX_SIZE) {
        distSize = MAX_SIZE;
    }
    if (device_width < MIN_DESIGN_WIDTH) return;
    setFontSize(Math.round(distSize));
};

window.addEventListener('resize', calc);

document.addEventListener('DOMContentLoaded', calc);

window.rem = function (size) {
    return size / BASE_SIZE + 'rem';
};

window.renderPx = function (size) {
    return Math.round((size / BASE_SIZE) * fontSize);
};