Promise string is not assignable to string

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The error message “Promise string is not assignable to string” occurs when there is an attempt to assign a promise object to a variable that is expecting a string.

In JavaScript, a Promise is an asynchronous operation that may or may not have completed yet. It represents the eventual completion (or failure) of an operation and allows us to handle the result (or error) in a more controlled manner.

Let’s look at an example to understand the error:


    // Example 1
    let myString = Promise.resolve("Hello World");
    let myVariable = myString; // Error: Promise string is not assignable to string

In the above example, we are trying to assign a Promise object (myString) to a variable (myVariable) expecting a string. This will result in an error because the types do not match.

To fix this error, we need to wait for the Promise to resolve and then assign its resulting value to the variable. We can achieve this using the .then() method or by using async/await syntax:


    // Example 2 - Using .then()
    let myStringPromise = Promise.resolve("Hello World");
    myStringPromise.then(result => {
      let myVariable = result; // Assign the resolved value to the variable
      console.log(myVariable); // Output: "Hello World"
    });

    // Example 3 - Using async/await
    async function assignString() {
      let myStringPromise = Promise.resolve("Hello World");
      let myVariable = await myStringPromise; // Wait for the promise to resolve and assign the value
      console.log(myVariable); // Output: "Hello World"
    }

    assignString();

In Example 2, we use the .then() method to handle the resolved value of the Promise and assign it to the variable. Similarly, in Example 3, we create an async function and use the await keyword to wait for the Promise to resolve before assigning the value.

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