javascript - 在函数外部使用 jquery 变量

Question

如何在声明变量的函数之外使用变量？

想要编辑完整代码，以获得更多帮助。

$(document).ready(function(){
    var bank_id = null;
    var purpose_id = null;
    $('#bank_id').on('change',function(e)
    {
        bank_id = e.target.value;
    });

    $('#purpose_id').on('change',function(e)
    {
        purpose_id = e.target.value;
    });

    var data = {
        "purpose_id" : purpose_id,
        "bank_id" : bank_id
    };

    $.post("financialLoans/getRates", data, function(result){
    });



});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<select class="form-control" required="" id="bank_id" name="bank_id"><option selected="selected" value="">Select</option><option value="1">Foo.</option><option value="2">bar</option>
</select>
<select class="form-control" required="" id="purpose_id" name="purpose_id"><option selected="selected" value="">Select</option><option value="1">Foo.</option><option value="2">bar</option>
</select>

Answer 1

您可以在所有函数之外(与全局作用域相同)使用 var 来声明全局变量。
注意:var 将在变量所在的位置作用域，函数之外是全局作用域(或 window 对象，与第二个示例相同)>

var myGlobalVariable;
$('#bank_id').on('change',function(e) { ... });

或者，您可以使用window属性:

$('#bank_id').on('change', function(e) {
    window.myGlobalVariable = ...
});

<小时/>片段示例:

//global variable
var globalVar = null;

$(document).ready(function(){
    //NOTE: bank_id is inside $(document).ready() scope, not global. But you still can use bank_id whenever you want inside this one.
    var bank_id = null;
    
    $('#bank_id').on('change',function(e) {
      //using bank_id inside $(document).ready() scope! :)
      bank_id = parseInt(e.target.value);
      globalVar = e.target.value;
    });
    
    $('#another_input').on('change', function(e) {
      //checking bank_id in another function! :D
      if(bank_id == 1){
        alert("Second input: " + e.target.value + " and bank_id is 1!");
      }else{
        alert("bank_id isn't 1. :(");
      }
      alert("Global variable changed too, it was null, and now have the same value as bank_id.\nCalling by name: " + globalVar + ".\nAnd calling by window object: " + window.globalVar + ".");
    });
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

<input type="text" id="bank_id"/>
<input type="text" id="another_input"/>