为什么我的函数在单击 onclick 之前触发?

Why is my function firing before the onclick is clicked?

下面是我的代码。在单击按钮之前,我的 getQuote 一直在触发。它在页面加载时立即触发。我觉得很奇怪,知道为什么吗?

function _(id) {
  return document.getElementById(id);
}
var html = "";
const newQuote = document.getElementById("submit");
const tweet = _("tweet-quote");
var tweetURL = "https://twitter.com/intent/tweet?hashtags=RonSwanson&text=";

newQuote.onclick = getQuote();

//Get Quote Function

function getQuote() {
  var ourRequest = new XMLHttpRequest();
  ourRequest.open('GET', 'https://ron-swanson-quotes.herokuapp.com/v2/quotes')
  ourRequest.onload = () => {
    var ourData = JSON.parse(ourRequest.responseText);
    quoteText = ourData[0];
    html = "<i class='fas fa-quote-left'></i>"
    html += ourData[0] + "<i class='fas fa-quote-right'></i>";
    html += "<br><br>" + "<p class='text-right'> -Ron Swanson</p>";
    _("quote").innerHTML = html;
    tweet.setAttribute('href', tweetURL + encodeURIComponent('"' + quoteText + '"') + encodeURIComponent("-Ron Swanson"));
  }
  ourRequest.send();
}

改变这个: newQuote.onclick = getQuote();

对此: newQuote.onclick = 获取报价单;