How to timeout a long-running promise

promise_race_timout.js

/**
  Credit: Kyle Simpson
  https://github.com/getify/You-Dont-Know-JS/blob/master/async%20&%20performance/ch3.md#never-calling-the-callback
*/

// A utility for timing out a Promise
function timeoutPromise(delay) {
    return new Promise( function(resolve,reject) {
        setTimeout( function() {
            reject( "Timeout!" );
        }, delay );
    } );
}

// setup a timeout for `foo()`
Promise.race( [
    foo(),                  // attempt `foo()`
    timeoutPromise( 3000 )  // give it 3 seconds
] )
.then(
    function(){
        // `foo(..)` fulfilled in time!
    },
    function(err){
        // either `foo()` rejected, or it just
        // didn't finish in time, so inspect
        // `err` to know which
    }
);