javascript - Wait for setTimeout to complete then proceed to execute rest of the code

Question

function sendMessage(){

        ...

        if(file){
            sendingMessage = true;
            setTimeout(() => {              
                sendingMessage = false;
                messages = [...messages, chatmessage];
            }, 3800)            
        }
        chatmessage = '';
        inputRef.focus()
        updateScroll();
    }

Right now when this function is called, chatmessage is first set to an empty string, etc. then the code in the timeout function is executed which is the corect behaviour. However, is there a way make setTimeout synchronous?

This is the behaviour I want:

1. If if(file) is true, set sendingMessage = true (sendingMessage triggers a spinning wheel animation)
2. Wait for 3.8 seconds and execute the content in the timeout function.
3. Only then, set chatmessage to empty string, etc (rest of the code)

Edit 1: I can just move the code inside the timeout function but the issue is in my case, if file is not present, it should just skip the timeout function alltogether. Then I would have to write another if block to check if the file is not present to execute the same commands (duplicate code). Another way to solve this would be to put the same code in a function and call it both places but feel like its not the ideal way to go and creating a function to change the value of three variables seems like overkill.

标签： javascript

Answer 1

You could make use of a Promise to wait for 3 seconds before executing the code.

For this to work, create a function that returns a promise which resolves after 3 seconds.

function wait(seconds) {
   return new Promise(resolve => {
      setTimeout(resolve, seconds * 1000);
   });
} 

Then inside the sendMessage function, call this function, passing in the number of seconds you want to wait. When the promise returned by this wait function resolves, execute the code that you want to execute after wait time is over.

Following code shows an example of how you coulc call wait function inside sendMessage function.

async function sendMessage() {

    ...

    if(file){
        sendingMessage = true;
   
        await wait(3);          // wait for 3 seconds

        sendingMessage = false;
        messages = [...messages, chatmessage];      
    }

    chatmessage = '';
    inputRef.focus()
    updateScroll();
}