JavaScript for…in vs for

Question

Do you think there is a big difference in for...in and for loops? What kind of \"for\" do you prefer to use and why?

Let\'s say we have an array of associative array

Answer 1

There is an important difference between both. The for-in iterates over the properties of an object, so when the case is an array it will not only iterate over its elements but also over the "remove" function it has.

for (var i = 0; i < myArray.length; i++) { 
    console.log(i) 
}

//Output
0
1

for (var i in myArray) { 
    console.log(i) 
} 

// Output
0 
1 
remove

You could use the for-in with an if(myArray.hasOwnProperty(i)). Still, when iterating over arrays I always prefer to avoid this and just use the for(;;) statement.