Jquery 在我包含严格模式之前，代码工作正常

Question

一段 Jquery 代码工作得很好，直到 "superiors" 告诉我必须在我的所有 Javascript 代码中包含严格模式。除了这段代码外，我的 main.js 文件一切正常。我无法重新识别错误，但每次激活脚本时都会触发我的控制台错误，它是一个 Boostrap 4 切换按钮，它确实打开了一个菜单，但菜单从上到下打开并且非常缓慢。按钮应该从右向左折叠。

$(function(){
    // mobile menu slide from the left
    $('[data-toggle="collapse"]').on('click', function() {
        $navMenuCont = $($(this).data('target'));
        $navMenuCont.animate({'width':'toggle'}, 280);
    });
})

控制台报错如下：

Uncaught ReferenceError: $navMenuCont is not defined
    at HTMLButtonElement.<anonymous> (main.js:61)
    at HTMLButtonElement.dispatch (jquery-3.3.1.js:5183)
    at HTMLButtonElement.elemData.handle (jquery-3.3.1.js:4991)

Answer 1

来自 MDN 参考：

First, strict mode makes it impossible to accidentally create global variables. In normal JavaScript mistyping a variable in an assignment creates a new property on the global object and continues to "work" (although future failure is possible: likely, in modern JavaScript). Assignments, which would accidentally create global variables, instead throw an error in strict mode.

您需要声明您的 $navMenuCont 变量。例如：

var $navMenuCont = $($(this).data('target'));

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

Jquery 在我包含严格模式之前，代码工作正常

Jquery code working fine until I included strict mode

javascript

jquery

strict