calling an object method with a setTimeout function from within the same object in Javascript

Question

OBeen bangin my head against the desk with this one and I have tried the answers I find on SE. Please help.

I have a function that polls an api for new data. All I want is for the function to repeat itself every 10000 ms. I thought the following would work:

    //SURVIVORS_OBJECT
//Store the suvivor object and append the map markers and some additional parameters to it
var survivorMarkers;
function dz_survivorMarkers(){
    //The survivors will be stored as an 'armaMapMarker' object 
    this.survivors = {};
    //Clear a survivor from the list because by id (eg: has not been returned in our query)
    this.clearSurvivor = function(pId){
        this.survivors[pId].marker.setMap(null);
        delete this.survivors[pId];
    };
    //make the api request from the overwatch data api
    this.getSurvivorsRequest = function(){
        console.log('UDBG:::survivorMarkers.getSurvivors ENTERED');
        //the callback function is passed as well
        api.getSurvivors(this.setSurvivors)
    };
    //Set survivors
    //This is the big one - here we will loop through all our existing survivors and check
    //  if they have been returned in the new reponse. If so, we will update their position on
    //  the map and add a poly line from their last position to their new one
    //We will also check if their info window is open, and will open it again for the user
    //The detail window will be checked if it is open too, and it's contents will be refreshed
    this.setSurvivors = function(pResponse) {
        console.log('UDBG:::survivorMarkers.setSurvivors ENTERED');
        console.log(pResponse);
//          try {
            if(pResponse.errors.length > 0) {
                exceptionHandler.e('SRV100',pResponse.errors.message);  
            } else {
                //First go through all our existing survivors, and see if they are in this request too
                var newSurvivors = {};
                for(var id in pResponse.records) {
                    //console.log('UDBG:::survivorMarkers.setSurvivors looping through survivor[' + id + ']');
                    var newSurvivor = new armaMapMarker('SURVIVOR', pResponse.records[id]);

                    //check if this record is in our existing list of survivors
                    if(this.survivors != null && this.survivors[id] != null) {
                        //set our interface options if any
                        newSurvivor.detailWindowIsOpen = this.survivors[id].detailWindowIsOpen;
                        newSurvivor.infoWindowIsOpen = this.survivors[id].infoWindowIsOpen;
                        //And clear the old data
                        this.clearSurvivor(id);
                    }
                    newSurvivors[id] = newSurvivor;
                }
                //Now go through all our old survivors, and see if they were NOT in the response and can be removed
                for(var id in this.survivors) {
                    if(pResponse.records[id] == null) {
                        this.clearSurvivor(id);
                    }
                }
                this.survivors = newSurvivors;
            }
//          } catch (e) {
//              alert(e);   
//          }
        setInterval(function(){survivorMarkers.getSurvivorsRequest()},5000);
    }
}

It will run once, but the second time will get an exception:

Uncaught TypeError: Object [object global] has no method 'clearSurvivor'

Answer 1

Nowhere is survivorMarkers defined, only declared. If you mean to call on the new instance, you will need to do something along the following lines. You also will want to change the setInterval to setTimeout as otherwise, you would be generating a new interval upon each API call completion, rather than generating a single new request upon the completion of a prior one. Hence we have the following.

setTimeout(function(){
    this.getSurvivorsRequest();
}.bind(this), 5000);

Or perhaps:

var thiz = this;
setTimeout(function(){
    thiz.getSurvivorsRequest();
}, 5000);

Lastly, your passed callback, this.setSurvivors is not bound to the instance and so is instead called on the global, fix this with api.getSurvivors(this.setSurvivors.bind(this)) .

Answer 2

您创建的对象实例应该是this.getSurvivorsRequest()而不是survivorMarkers 。