如何在 jQuery 选择器中使用 JavaScript 变量？

(function($){

var words = $('#readpcd').text().match(/(\w+)/g);
if (words.length) {
    var lastword = words[words.length - 1];
}
console.log(lastword);
 
$('select option[value=" + this.lastword +"]').attr("selected","selected");


}(jQuery || window.jQuery));

我试过了

$('select option[value="${lastword}"]').attr("selected","selected");