There are two initialisation and no "x<y" to limit the iterations. So how does this loop work?
var features = [{
position: new google.maps.LatLng(-33.91721, 151.22630),
type: 'info'
}, {
position: new google.maps.LatLng(-33.91539, 151.22820),
type: 'info'
}, {
position: new google.maps.LatLng(-33.91747, 151.22912),
type: 'info'
}];
for (var i = 0, feature; feature = features[i]; i++) {
addMarker(feature);
}
Access to an out-of-bound index in Javascript will yield undefined, which is a falsey value. Once the index has got outside of the bound, the feature = features[i] assignment, which evaluates to the value it assigns, will be considered false and the loop will exit.
There is a shortcut where if you wish to assign and return same value, you can do return variable = value. This will return value
Sample
var x;
function notify(v){
return x = v;
}
console.log(notify(10))So in your code, when you do feature = features[3], since features[3] is undefined, it returns undefined which is falsey. Hence your loop breaks.
Sample
var x = 0;
if(x = 1){
console.log('Success')
}
else{
console.log('Error')
}
if(x = undefined){
console.log('Success')
}
else{
console.log('Error')
}Note you loop will break if features[i] return 0 or false or undefined or any other falsey value. This is working fine in this case, but I would not recommend it.
featurewill always equalfeatures[i], andi++still increments. This should still loop over 3 times.forloop,for(initialization; condition; final-expression)i=3features[i] will returnundefinedand that will break the loopfeatures.forEach(addMarker), Of course you wanted to know why it worked, but for people browsing might be worth pointing out the forEach.forEachor any other method would be out of scope. But for anyone who is looking for it, please refer Different ways to loop through array