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The next thing I'd like to talk about is arrays. This brings some of the elements together of the previous two sections. In JavaScript, you can have very large arrays. And you can have arrays that are sparse, that  don't have every element inside of them. And so V8 actually has two different methods to handle two different types of arrays. The first one is fast elements. And fast elements, they have a linear storage buffer. And V8 uses them if the set of keys for the array is very compact.

  If that's not the case-- so you have a very sparse array-- then it uses a different format, which is dictionary elements. Fast elements, linear buffer, very fast and efficient to access. Dictionary elements, it's a hash table.

 Much more compact but also more expensive at run time to access.

  Kind of obvious here, if you want to have your arrays be very fast, make sure that V8 uses fast elements to represent them. And the way to do this is to make sure that your keys start at zero and that they're contiguous.

 So don't create an array and start using index number 25,000.  Start at zero and go up.

 Also, don't allocate really large arrays that you're not going to use everything in. So if you allocate an array with 65,000 elements and you

 only use the first five, V8 thinks, well, that's a very sparse array, and will switch into dictionary mode, which  means the access of the elements will be slower. Don't delete elements inside of arrays. Same principle here, because when you delete elements, it makes the key set sparse. And it can lead to V8 switching the elements to dictionary mode. Don't load from uninitialized or deleted elements. This is an important one. It's easy to get wrong.  (총 단어수: 305)

The next thing I'd like to talk about is arrays. This brings some of the elements together of the previous two sections. In JavaScript, you can have very large arrays. And you can have arrays that are sparse, that  don't have every element inside of them. And so V8 actually has two different methods to handle two different types of arrays. The first one is fast elements. And fast elements, they have a linear storage buffer. And V8 uses them if the set of keys for the array is very compact.

  If that's not the case-- so you have a very sparse array-- then it uses a different format, which is dictionary elements. Fast elements, linear buffer, very fast and efficient to access. Dictionary elements, it's a hash table.

 Much more compact but also more expensive at run time to access.

  Kind of obvious here, if you want to have your arrays be very fast, make sure that V8 uses fast elements to represent them. And the way to do this is to make sure that your keys start at zero and that they're contiguous.

 So don't create an array and start using index number 25,000.  Start at zero and go up.

 Also, don't allocate really large arrays that you're not going to use everything in. So if you allocate an array with 65,000 elements and you

 only use the first five, V8 thinks, well, that's a very sparse array, and will switch into dictionary mode, which  means the access of the elements will be slower. Don't delete elements inside of arrays. Same principle here, because when you delete elements, it makes the key set sparse. And it can lead to V8 switching the elements to dictionary mode. Don't load from uninitialized or deleted elements. This is an important one. It's easy to get wrong.  (총 단어수: 305)