Correct way to break out of if statement within for loop

Question

What is the correct way of breaking out of a nested if statement/for loop? I have tried the following approach but the preferred approach does not work:

service.js - NOT WORKING but better because it breaks out as soon as a match is found

    getSelectedService: function(serviceId) {
        serviceId = parseInt(serviceId);
        for(i=0;i<servicesData.length;i++) {
            if(servicesData[i].id === serviceId) {
                var service = servicesData[i];
                return service;
            }
        }
    }

services.js - WORKING but not good as it loops through everything even when a match is found

getSelectedService: function(serviceId) {
    serviceId = parseInt(serviceId);
    servicesData.forEach(function(service) {
        if(service.id === serviceId) {
            var selectedService = service;                  
        }
    });
    return selectedService;
}

The first code returns the first matched service, the second returns the last matched service. It's not obvious what "NOT WORKING" means. They are equivalent and most likely identical. — zerkms
– zerkms, Commented Jan 18, 2016 at 3:28
Use filter. getSelectedService: function(serviceId) { serviceId = parseInt(serviceId); var service = servicesData.filter(service => service.id === serviceId); return service.length ? service[0] : {}; } — Tushar
– Tushar, Commented Jan 18, 2016 at 3:29
@Tushar why would one prefer your suggestion over the first code example? And as soon as you use ES2015 - why not use Array.prototype.find()? — zerkms
– zerkms, Commented Jan 18, 2016 at 3:30
@zerkms you're right. I looked elsewhere and found the problem — methuselah
– methuselah, Commented Jan 18, 2016 at 3:37

Corentin Bruneau · Accepted Answer · 2016-01-18 03:38:35Z

1

If you want to stop on the first match, you shoud use a while loop.

var keepGoing = true;
var i = 0;
var service;

while( keepGoing && i < servicesData.length ) {
    if( servicesData[i].id === serviceId ) {
        service = servicesData[i];
        keepGoing = false;
    } else {
        i++;
    }
}

return service;

answered Jan 18, 2016 at 3:38

Corentin Bruneau

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2 Comments

jfriend00 Over a year ago

@methuselah - There's no fundamental reason a while loop is better than a for loop for this purpose. The two can be used fairly interchangeably. You can break out of a for loop with break or return just fine.

Corentin Bruneau Over a year ago

I agree, I just gave an answer different from the solutions he tried.

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