JQuery控制器URL拼接问题：接口返回空数组求助

Let's break down the issues here step by step—your empty monthData is likely due to a couple of easy-to-fix mistakes:

1. Critical Variable Mix-Up (The Main Culprit) #

You stated you want the final URL to be /api/ExpiationsWebAPI?category=01&year=2017, but your variable assignments are reversed:

var yearReturned = 01; // This should be 2017
var categoryReturned = 2017; // This should be 01

This means your constructed URL is actually ?category=2017&year=01—the API is almost certainly returning no data because these parameter values don't match any valid records.

2. Other Potential Issues to Fix #

• Undeclared monthData: You’re assigning monthData = graphData; without declaring it first, which makes it a global variable (bad practice, and can lead to unexpected behavior). Always declare variables with var, let, or const.
• Redundant document.ready Nesting: $(function graphDataIn() { ... }) is just a shorthand for $(document).ready(), so nesting it inside another $(document).ready() is unnecessary and can delay execution.
• Unnecessary new String: var controlUrl = new String; is overcomplicating things—just initialize it as an empty string or directly build the URL.
• Legacy success Callback: While it works, the success parameter in jQuery AJAX is legacy; modern code uses the done() method instead.

Corrected Code #

Here's the fixed version that addresses all these issues:

// Correct variable assignments (use string for category to preserve leading zero if needed)
var categoryReturned = "01";
var yearReturned = 2017;
// Directly build the URL without unnecessary initialization
var controlUrl = "/api/ExpiationsWebAPI?category=" + categoryReturned + "&year=" + yearReturned;

// Proper document ready handler (no nesting)
$(document).ready(function () {
  // Declare monthData in the correct scope
  let monthData = [];

  function graphDataIn() {
    $.ajax({
      type: "GET",
      url: controlUrl,
      dataType: "json" // Explicitly request JSON to avoid parsing issues
    })
    .done(function (graphData) {
      console.log("Graph Data loaded", graphData);
      monthData = graphData;
      alert("Success");
    })
    .fail(function (xhr, status, error) {
      // Log error details for easier debugging
      console.error("AJAX Failed:", status, error);
      alert("Fail: " + error);
    })
    .always(function () {
      alert("Complete");
    });
  }

  // Call the function to trigger the request
  graphDataIn();
});

Quick Debugging Tip #

Add console.log(controlUrl); right after building the URL to verify it matches your expected format before sending the request—this will catch variable mix-ups instantly.

内容的提问来源于stack exchange，提问作者Steven Hale