2008年10月31日 · Append has (amortized) constant time complexity, O (1). Extend has time complexity, O (k). Iterating through the multiple calls to .append() adds to the complexity, making it equivalent to that of extend, and since extend's iteration is implemented in C, it will always be faster if you intend to append successive items from an iterable onto a list.

Note that some languages call this method defaults or inject, as it can be thought of as a way of injecting b's values (which might be a set of default values) in to a dictionary without overwriting values that might already exist. Of course, you could simple note that a.extend(b) is nearly the same as b.update(a); a=b.

ary.extend (ext) merely adds reference to "ext" list to the end of the "ary" list, resulting in less memory transactions. As a result, .extend works orders of magnitude faster and doesn't use any additional memory outside of the list being extended and the list it's being extended with.

2013年12月18日 · The extend method for example in jQuery or PrototypeJS, copies all properties from the source to the destination object. Now about the prototype property, it is a member of function objects, it is part of the language core. Any function can be used as a constructor, to create new object instances. All functions have this prototype property. When you use the new …

2020年9月8日 · I saw this in a plugin: var options = $.extend(defaults, options); How does it work? What does extend() do?

In order to prevent having to specify all of the settings within the config object, I use jQuery's extend method to fill in a new object, settings with any default values from the default object if they weren't specified in the config object:

2009年9月3日 · To extend an existing JavaScript array with another array without creating a new one, you can use the push () method combined with the spread operator .... Here’s how:

2008年10月1日 · The big win in this response is how extend can apply methods as class or instance methods, depending on utilization. Klass.extend = class methods, objekt.extend = instance methods. I always (wrongly) assumed class …

Well.. for $.extend you need to have jQuery available. So the one difference is that one of them depend on an external library. If you already have jQuery in your project this point is kinda moot - but including an entire library just so that you can use one $.extend function doesn't seem like such a good idea.

2012年5月3日 · No need to use any external library to extend In JavaScript, everything is an object (except for the three primitive datatypes, and even they are automatically wrapped with objects when needed).