JSFiddle - React, Tailwind, and code Playground
HTML
<input type="checkbox" onchange="showData(this)"> select
JavaScript
var a = '';
var b = '';
function ajax_test(){
$.ajax({
url:"https://swapi.co/api/people/1",
success: function(data, status, xhr){
a = data.height;
b = a + " lala"
}
});
}
function showData(tha){
if (tha.checked) {
alert(b);
}
}
ajax_test();//init