获取系统时间、本地存储、比较日期并执行操作

Question

我需要获取一次系统时间，然后将其存储在localStorage上，然后将存储的值与其他系统日期进行比较，如果未来日期等于或大于存储的日期，则执行操作。我试过了，但我被困在了这个函数中，这个函数第一次让系统时间只运行一次，这样我就可以得到一个未来的日期来进行比较。这是我的代码

console.log(formatTime());
function formatTime() {
var date = new Date();
var hours = date.getHours();
var minutes = date.getMinutes();
var seconds = date.getSeconds();
var ampm = hours >= 12 ? "PM" : "AM";
hours = hours % 12;
hours = hours ? hours : 12; // the hour '0' should be '12'
minutes = minutes < 10 ? "0" + minutes : minutes;
return (strTime = date.getDay() + "/" + date.getMonth() + "/" + date.getFullYear() + " " + hours + ":" + minutes + ":" + seconds + " " + ampm);
}
document.getElementById("currentdt").innerHTML = strTime;
var strTime1 = formatTime();
var timeString = JSON.stringify(strTime1);
localStorage.setItem("strTime1", timeString);
var timeStringFromLocalStorage = localStorage.getItem("strTime1");
var timeFromLocalStorage = JSON.parse(timeStringFromLocalStorage);
document.getElementById("time").innerHTML = strTime1;
console.log(timeStringFromLocalStorage);
function compare(dateTimeA, dateTimeB) {
var momentA = moment(dateTimeA, "strTime1");
var momentB = moment(dateTimeB, "strTime");
if (momentA > momentB) return 1;
else if (momentA < momentB) return -1;
else return 0;
}
alert(compare("strTime1", "strTime"));

Answer 1

下面的函数将检查localStorage中是否设置了值。如果没有设置值，它将设置第一个值并停止该功能。

如果有一个值，那么它将被转换为moment实例，并与当前日期进行比较。如果天数差等于或大于指定的，则会重定向页面。

function redirectWhenOlderThan(days, url) {
const storedValue = localStorage.getItem('first-visit');
const now = moment();

/**
* If nothing is stored yet, then storedValue will be null.
* Here you will set the first localStorage item for the first time.
* Instead of a full date, store the timestamp.
* Then stop the function.
*/
if (storedValue === null) {
localStorage.setItem('first-visit', now.valueOf().toString());
return;
}
/**
* If there is a stored value then it will be a timestamp as a string.
* First parse it into a number before putting it into moment.
* Then check the difference in days between the dates.
*/
const then = moment(Number(storedValue));
const difference = now.diff(then, 'days');
/**
* If the difference is higher or equal to the given days, redirect.
*/
if (difference >= days) {
location.href = url;
}
}

使用自第一次访问以来应该经过的天数和要重定向到的URL调用函数。

redirectWhenOlderThan(15, 'https://example.com');

我希望这就是你的意思。

旁注：如果有时间，请深入moment.js。它有很多功能可以让你节省一些时间，比如你的formatTime()函数，它可以随时写在一行中。

moment().format('DD/MM/YYYY h:mm:ss A');

Answer 2

现在最后的代码如下

function formatTime() {
var date = new Date();
return strTime = date.getDay() + '/' + date.getMonth()+'/'+date.getFullYear();
}
document.getElementById("currentdt").innerHTML = strTime;

function redirectWhenOlderThan(days, url) {
const storedValue = localStorage.getItem('first-visit');
const now = moment();
if (storedValue === null) {
localStorage.setItem('first-visit', now.valueOf().toString());
return;
}
const then = moment(Number(storedValue));
const difference = now.diff(then, 'days');

if (difference >= days) {
location.href = url;
}
else {
window.location.href= 'app/phr.html';
}
}
setTimeout(function () {
redirectWhenOlderThan(1, 'app/licences.html');
}, 3000);