Javascript语句满足所有条件可能会出错

Question

这段代码满足所有条件，请有人告诉我哪里出错了；我检查过，看不出代码有什么问题。为什么所有条件都满足。

<script>
$( document ).ready(function() {
    var style = $('#el_teams_TeamFormation span').html(); 
    alert (style);
         if (style = "4-4-2")
          { 
            document.getElementById('footballpitch1').style.display = "none";
            document.getElementById('footballpitch2').style.display = "none";
            document.getElementById('footballpitch3').style.display = "none";
            document.getElementById('footballpitch4').style.display = "none";
            document.getElementById('footballpitch1').style.display = "block";
         }
         if (style = "3-4-3")
          {
            document.getElementById('footballpitch1').style.display = "none";
            document.getElementById('footballpitch2').style.display = "none";
            document.getElementById('footballpitch3').style.display = "none";
            document.getElementById('footballpitch4').style.display = "none";
            document.getElementById('footballpitch2').style.display = "block";
         } 
         if (style = "3-5-2") {
            document.getElementById('footballpitch1').style.display = "none";
            document.getElementById('footballpitch2').style.display = "none";
            document.getElementById('footballpitch3').style.display = "none";
            document.getElementById('footballpitch4').style.display = "none";
            document.getElementById('footballpitch3').style.display = "block";
         }
         if (style = "4-5-1") {
            document.getElementById('footballpitch1').style.display = "none";
            document.getElementById('footballpitch2').style.display = "none";
            document.getElementById('footballpitch3').style.display = "none";
            document.getElementById('footballpitch4').style.display = "none";
            document.getElementById('footballpitch4').style.display = "block";
         }
});

Answer 1

值得您熟悉不同类型的比较运算符:

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Comparison_Operators

简单来说，单等号 (=)、双等号 (==) 和三等号 (===) 各自表示不同的含义到 JavaScript。

单个 = 是一个赋值运算符，因此在每个 if 语句中，您实际上是要求脚本将值“4-4-2”(依此类推)分配给变量 style 而不是比较两个值。

如果您使用 == (带类型强制)或 === (无强制)，您的代码应该可以正常工作。