javascript - 如何在 Fetch API 响应之外访问 JSON 对象？

Question

这个问题已经有答案了:

How do I return the response from an asynchronous call? (42 个回答)

已关闭 6 年前。

我目前在访问 emoji_map 时遇到问题then之外范围，但我不知道该怎么做。

这是我的代码:

if (req) {
    fetch(req).then(function(response) {
        return response.json();
    }).then(function(response) {
    /* start to observe */
    emoji_map = response.emoji_map;
    console.log(emoji_map);
    });

}

当我执行 console.log(emoji_map); 时在 if 循环之外我无法访问分配的响应。有人可以帮忙吗？

Answer 1

我建议您在 MDN 上阅读有关 JavaScript 词法作用域和闭包的更多信息:https://developer.mozilla.org/en-US/docs/Web/JavaScript/Closures .

function init() {
  var name = "Mozilla"; // name is a local variable created by init
  function displayName() { // displayName() is the inner function, a closure
    alert(name); // use variable declared in the parent function    
  }
  displayName();    
}
init();

init() creates a local variable name and then a function called displayName(). displayName() is an inner function that is defined inside init() and is only available within the body of that function. displayName() has no local variables of its own, however it has access to the variables of outer functions and so can use the variable name declared in the parent function.