modernJS/promises.html at master · yfain/modernJS · GitHub

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<!DOCTYPE html>
<html>
<head>
    <title>promises.html</title>
</head>
<body>


<script>

    'use strict';

    /*
     function getProductDetails() {

      setTimeout(function () {
        console.log('Getting customers');
        setTimeout(function () {
          console.log('Getting orders');
          setTimeout(function () {
            console.log('Getting products');
            setTimeout(function () {
              console.log('Getting product details')
            }, 1000);
          }, 1000);
        }, 1000);
      }, 1000);
     };

     getProductDetails();
     */

    function getCustomers(){

        let promise = new Promise(
                function (resolve, reject){

                    console.log("Getting customers");
                    // Emulate an async server call here
                    setTimeout(function(){
                        let success = true;
                        if (success){
                            resolve( "John Smith"); // got the customer
                        }else{
                            reject("Can't get customers");
                        }
                    },1000);

                }
        );
        return promise;
    }

    function getOrders(customer){

        let promise =  new Promise(
                function (resolve, reject){

                    // Emulate an async server call here
                    setTimeout(function(){
                        let success = true;
                        if (success){
                            resolve( `Found the order 123 for ${customer}`); // got the order
                        }else{
                            reject("Can't get orders");
                        }
                    },1000);

                }
        );
        return promise;
    }


    getCustomers()
            .then((cust) => {console.log(cust);return cust;})
            .then((cust) => getOrders(cust))
            .then((order) => console.log(order))
            .catch((err) => console.error(err));
    console.log("Chained getCustomers and getOrders. Waiting for results");
</script>

</body>
</html>