如果用户关闭选项卡，则发布请求，Vuejs

Question

如果用户尝试关闭选项卡或更改路线，我会尝试发出发布请求。但是我得到一个变量的空值。detectTabClose() {  let newValues = {    question: this.question_id,    user_id: this.$userId  //this is global, from root and is ok  };  window.addEventListener("beforeunload", function(e) {    var confirmationMessage = "o/";    (e || window.event).returnValue = confirmationMessage;    console.log(this.question_id);  //I get undefined    axios      .post("/submit/answer", newValues)      .then(() => {        console.log("Post before tab closing");      })      .catch(() => {        console.log("Error on post");      });    return confirmationMessage;  });},

Answer 1

您无法访问this.question_id内部的原因window.addEventListener是您没有使用箭头功能。在您现在的情况下，this关键字指向事件而不是 vue 实例。

如果将此箭头函数用于侦听器事件，则可以访问question_id.

detectTabClose() {

  let newValues = {

    question: this.question_id,

    user_id: this.$userId  //this is global, from root and is ok

  };

  window.addEventListener("beforeunload", (e) => {

    var confirmationMessage = "o/";

    (e || window.event).returnValue = confirmationMessage;

    console.log(this.question_id);  // this will be accessible now

    axios

      .post("/submit/answer", newValues)

      .then(() => {

        console.log("Post before tab closing");

      })

      .catch(() => {

        console.log("Error on post");

      });

    return confirmationMessage;

  });

},