如果您正在ajax成功处理程序中执行$.parseJSON(data) ，因为您正在ajax中执行$.parseJSON(data)成功处理程序，问题几乎可以肯定是jQuery已经已经为您解析了它. jQuery将查看响应的Content-Type，如果响应为application/json，它将对其进行解析，并将解析的结果提供给成功处理程序.如果将其传递给$.parseJSON，将会发生的第一件事是它将被转换回字符串(对于您来说是"[object Object]")，然后$.parseJSON将无法解析该字符串.

If you're doing the $.parseJSON(data) in an ajax success handler Since you're doing the $.parseJSON(data) in an ajax success handler, the problem is almost certainly that jQuery has already parsed it for you. jQuery will look at the Content-Type of the response and, if it's application/json, it will parse it, and provide the parsed result to your success handler. The first thing that will happen if you pass that into $.parseJSON will be that it will get converted back to a string ("[object Object]", in your case), which $.parseJSON will then fail to parse.

只需按原样使用data，就已经有了对象，这要归功于自动解析:

Just use data as-is, it's already an object, thanks to the automatic parsing:

$(document).ready(function() {
    $('#branchAndSubjects').click(function() {
        $.post('/findBranchAndSubjects', {
            roll: roll,
            _token: "{{csrf_token()}}"
        }, function(data) {
            console.log(data.year);             // 3
            console.log(data.subjects.length);  // 4
            console.log(data.subjects[0].name); // Control Systems
        });
    });
});