JSFiddle - React, Tailwind, and code Playground

HTML

<button id='bt1' />bt1</button>
<button id='bt2' />bt2</button>
<button id='bt3' />bt3</button>
<button id='bt4' />bt4</button>
<button id='bt5' />bt5</button>

JavaScript

var $ = function (id) {
    return document.getElementById('bt' + id);
}
for (var i = 1; i < 6; i++) {

    (function (i) {
        $(i).onclick = function () {
            alert(i);
        }
    })(i);
    /* 下面这种方法也能行，总之就是要把外层变量给存到本作用域中
    (function () {
       var j=i;
       $(j).onclick = function () {
            alert(j);
        }
    })();
    */
}