使用setTimeout在指定的超时后触发函数调用。

if (window.location.href.indexOf('/?edit') === -1) {
  const lang = window.navigator.language;
  const userLang = window.navigator.userLanguage;
  let pageLang = 'en';

  if (lang == "sv-SE" || userLang == "sv-SE") pageLang = 'se';

  window.setTimeout(() => {
    window.location.href += pageLang;
  }, 3000);
}

使用setTimeout或setInterval如下：

setTimeout(function(){ 
// any staff
},3000);

对你来说就像：

if (lang == "sv-SE" || userLang == "sv-SE") {
setTimeout(function(){ 
      window.location.href = window.location.href + "se";
},3000);
    } else {
setTimeout(function(){ 
      window.location.href = window.location.href + "en";
},3000);
    }

如果不想使用setTimeout，可以使用sleep()，

function sleep( millisecondsToWait )
{
    var now = new Date().getTime();
    while ( new Date().getTime() < now + millisecondsToWait )
    {
        /* do nothing; this will exit once it reaches the time limit */
        /* if you want you could do something and exit */
    }
}

console.log('something');
sleep(3000);
console.log('hello');