在另一个 function 的 if 语句中使用来自 fetch-api 的 promise 结果 - JS

Question

So I have this fetch-api

let test = () => fetch(usd_api).then(response => response.json())
.then(data => data.exchange_rates.dash_usd);

Console log

let console_test = () => {console.log(test())}

How can use this number [[PromiseResult]]: 134.445... in the following function where the number 150 is.

function main(){

         fetch(txs_api).then(response => response.json()).then(function(data) {
                
             var amount = data.txs[0].vout[1].value;
               
             if(amount == 150){
                // SUCCESS!
                $('#modal').modal('hide');
                console.log('requests stopped');
                clearInterval(interval);
             }
         })
}

Answer 1

let test = () => fetch(usd_api)
  .then(response => response.json())
  .then(data => data.exchange_rates.dash_usd);

You want too keep using the same promise, if you want to log the result of your promise you need to wait for it to be completed:

// with .then()
test().then(console.log);

// or with await if you can:
console.log(await test());

Answer 2

I figured it out. Don't know if it's the best way to do it but it's working.

function main(){

  fetch(usd_api).then(response => response.json()).then(function(data) {
                        
      var dash_price = data.exchange_rates.dash_usd;
                    
      fetch(txs_api).then(response => response.json()).then(function(data) {
                    
          var amount = data.txs[0].vout[1].value;

          if(amount == dash_price){
              // SUCCESS!
              $('#modal').modal('hide');
              console.log('requests stopped');
              clearInterval(interval);
          }
      })
   })
}

Answer 3

Do not return value. Because it returns to below function

function(data) {
  return data.exchange_rates.dash_usd
}

If you want to return your value to a variable you have to use Promise like below.

    let test = new Promise((resolve, reject) => {
        fetch(usd_api).then(response => response.json())
            .then(function (data) {
                resolve(data.exchange_rates.dash_usd) 
            });
    })
    
    async function demo(){
        let console_test  = await test
        console.log(console_test )
    }
    demo()

Note : Do not forget to use async and await