Chrome-remote-interface: How to get value by Runtime. evaluate without then()

[fh1994]

is it possible to get the outerHTML without then() method?
I can't output the outerHTML.
There is a delay because of promise, and the return(a) happened earlier than the console.log(a); I don't want to use SetTimeOut().
Here is my code...

function(){
var a;
Runtime.evaluate({expression:'document.documentElement.outerHTML'}).then((result)=>{                        

                        a = result.result.value;
                         **console.log(a);**

                    });

**return a;** 
}

[cyrus-and]

It's not a matter of using a promise here, all the methods of the protocol are inherently asynchronous so you must use one of the common JavaScript patterns used to serialize the execution of your asynchronous code. In fact you could have used the callback API in your code (still wrong):

function f() {
    var a;
    Runtime.evaluate({expression: 'document.documentElement.outerHTML'}, (error, result) => {
        a = result.result.value;
        console.log(a);
    });
    return a;
}

Callbacks

function f(callback) {
    Runtime.evaluate({expression: 'document.documentElement.outerHTML'}).then((result) => {
        const a = result.result.value;
        callback(null, a);
    }).catch((err) => {
        callback(err);
    });
}

// caller
f((err, result) => {
    if (err) {
        console.error(err);
    } else {
        console.log(result);
    }
});

Promises

function f() {
    return Runtime.evaluate({expression: 'document.documentElement.outerHTML'}).then((result) => {
        const a = result.result.value;
        return a;
    });
}

// caller
f().then((a) => {
    console.log(a);
}).catch((err) => {
    console.error(err);
});

Promises (with async/await)

// same f() as above

async function caller() {
    try {
        const a = await f();
        console.log(a);
    } catch (err) {
        console.error(err);
    }
}

caller();