Could someone tell me what I am doing wrong when I'm writing this promise? I want the first function in calculate to execute and then setState of the ponent after the calculations are plete.

var calculate = new Promise({

            function(resolve, reject) {
                var newSubtotal = 0;
                var newTotal = 0;

                this.props.cart.map((product)=>{

                    newSubtotal += product.price;
                    newTotal += product.price;
                    newTotal *= 1.10;

                });
                resolve(newSubtotal, newTotal);
            }
        });

        calculate.then(() => {
            this.setState({
              subtotal: newSubtotal,
              total: newTotal
            });
        });

Could someone tell me what I am doing wrong when I'm writing this promise? I want the first function in calculate to execute and then setState of the ponent after the calculations are plete.

var calculate = new Promise({

            function(resolve, reject) {
                var newSubtotal = 0;
                var newTotal = 0;

                this.props.cart.map((product)=>{

                    newSubtotal += product.price;
                    newTotal += product.price;
                    newTotal *= 1.10;

                });
                resolve(newSubtotal, newTotal);
            }
        });

        calculate.then(() => {
            this.setState({
              subtotal: newSubtotal,
              total: newTotal
            });
        });

• javascript
• reactjs

2 Answers 2

Because you are passing object but function is expected

it should be something like this

var calculate = new Promise(function(resolve, reject){
// some stuff
})

In your code

 calculate.then(() => {
        this.setState({
          subtotal: newSubtotal,
          total: newTotal
        });
    });

has no access to newSubtotal, newTotal.

How about?

 calculate.then((newSubtotal, newTotal) => {
        this.setState({
          subtotal: newSubtotal,
          total: newTotal
        });
    });

Also, add: reject(someFailCase);