如何从 JSON 字符串中提取值列表并遍历它们？

Question

我有一个国家到州的动态 JSON 地图。前任。 {"Canada":["Ontario","Quebec","Alberta"],"USA":["Michigan","Maine","New Hampshire"]}

我知道所选的国家/地区名称。

问题：如何从地图中获取所选国家名称的州列表并遍历值？

<script>
function onChangeCountry() {
    var selectedCountry = $('#country').find(":selected").text();
    alert("010 selectedCountry = "+ selectedCountry); // <<-- this gets me the selected country, works fine

    var jsonMapCountryToStates = ${jsonMapCountryToStates};
    alert("020 JSON.stringify(jsonMapCountryToStates) = "+JSON.stringify(jsonMapCountryToStates)); // <-- this shows me the whole map

    // how do I iterate through the list of states for 'selectedCountry' ?
}
</script>

Answer 1

也许将它们组成一个数组，然后就像其他数组一样。

let fundata = {"Canada":["Ontario","Quebec","Alberta"],"USA":["Michigan","Maine","New Hampshire"]};

console.log(Array.from(fundata.USA));

// or using the other syntax:
let namedPlace = "USA";
console.log(Array.from(fundata[namedPlace]));

一个例子中的更多动作：

var fundata = {
  "Canada": ["Ontario", "Quebec", "Alberta"],
  "USA": ["Michigan", "Maine", "New Hampshire"]
};


function onChangeCountry(e) {
  let selectedCountry = $(this).find(":selected").val();
  console.log("010 selectedCountry = " + selectedCountry);
  fundata[selectedCountry].forEach(element => console.log("State:", element));
}
for (const prop in fundata) {
  $('#country').append("<option value='" + `${prop}` + "'>" + `${prop}` + "</option>")
  console.log(`${prop}: ${fundata[prop]}`);
}

$("#country").on("change", onChangeCountry);

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<select id="country" />