Question

我声明了一个带有空数组值的变量 names ，然后在函数内部使用它来分配返回值，然后我想在函数之外使用它，但是在函数外面这个变量仍然是空的。请解释我做错了什么。

  handleUpdateInputBusinessName = (searchText) => {
    var names = [];
    var displaySuggestions = function(predictions, status) {
      if (status !== google.maps.places.PlacesServiceStatus.OK) {
        alert(status);
        return;
      }

      predictions.forEach(function(prediction) {
        let name = prediction.description;
        names.push(name);
      });

      console.log('names_in:', names); // valid predictions from Google Maps Service
      return names;    
    };

    console.log('names_out:', names); // []

    var service = new google.maps.places.AutocompleteService();
    service.getQueryPredictions({ input: searchText, types: '(cities)'    
    }, displaySuggestions);

Answer 1

这是简化版本：

＆＃13;

a = [];
var b = () => {
  a.push(1);
  console.log('inside:', a)
};
console.log('outside:', a);
b();

＆＃13;

＆＃34;外面＆＃34;控制台日志在调用displaySuggestions函数之前运行，因此数据尚未填充在数组中。

Answer 2

你必须使用js匿名函数语法来增加下面名称数组的范围是代码。

 handleUpdateInputBusinessName = (searchText) => {
    var names = [];
    var displaySuggestions = (predictions, status) => {
      if (status !== google.maps.places.PlacesServiceStatus.OK) {
        alert(status);
        return;
      }
  predictions.forEach((prediction) => {
    let name = prediction.description;
    names.push(name);
  });

  console.log('names_in:', names); // valid predictions from Google Maps Service
  return names;    
};

console.log('names_out:', names); // []

var service = new google.maps.places.AutocompleteService();
service.getQueryPredictions({ input: searchText, types: '(cities)'    
}, displaySuggestions);

希望这会好起来。

我不能使用变量功能

2 个答案: