空值操作符  		??		左侧操作数为null或者undefined时,返回右侧操作数
逻辑或操作符		||		左侧操作数为假值时,返回右侧操作数

var a = "1770013";
var arr = [];
var m = a.length % 3;
if (m !== 0) {
    arr.push(a.substring(0, m));
}
for (var i = 0; i < parseInt(a.length / 3); i++) {
    arr.push(a.slice(m + i * 3, m+ (i + 1) * 3))
}

//处理https请求
window.onload = function () {
    if (location.protocol === "https:") {
        location.href = location.href.replace("https://", "http://")
    }
};

获取url参数

function getUrlParams(key) {
    var query = window.location.search.substring(1);
    if (query) {
        var vars = query.split("&");
        for (var i = 0; i < vars.length; i++) {
            var pair = vars[i].split("=");
            if (pair[0] == key) {
                return pair[1];
            }
        }
    }
    return "";
}