What's the best/standard way of merging two associative arrays in javascript? Does everyone just do it by rolling their own for loop?
Source: Tips4all
Source: Tips4all
I have a 2.67 GHz Celeron processor, 1.21 GB of RAM on a x86 Windows XP Professional machine. My understanding is that the Android emulator should start fairly quickly on such a machine, but for me it does not. I have followed all instructions in setting up the IDE, SDKs, JDKs and such and have had some success in staring the emulator quickly but is very particulary. How can I, if possible, fix this problem?
with jquery you can call $.extend
ReplyDeleteobj1 = {a: 1, b: 2};
obj2 = {a: 4, c: 110};
obj3 = $.extend(obj1, obj2);
obj1 == obj3 == {a: 4, b: 2, c: 110}
(assoc. arrays are objects in js)
look here: http://api.jquery.com/jQuery.extend/
This is how Prototype does it:
ReplyDeleteObject.extend = function(destination, source) {
for (var property in source) {
if (source.hasOwnProperty(property)) {
destination[property] = source[property];
}
}
return destination;
};
called as, for example:
var arr1 = { robert: "bobby", john: "jack" };
var arr2 = { elizabeth: "liz", jennifer: "jen" };
var shortnames = Object.extend(arr1,arr2);
EDIT: added hasOwnProperty() check as correctly pointed out by bucabay in comments
In dojo, the 2-objects/arrays "merge" would be dojo.mixin(destination, source) -- you can also mix multiple sources into one destination, etc -- see the mixin function's reference for details.
ReplyDeleteIn Javascript there is no notion of
ReplyDeleteassociative array, there are objects
The only way to merge two objects is
to loop for their properties and
copy pointers to their values that
are not primitive types and values
for primitive types to another
instance
do you want to overwrite a property if the names are the same but the values are not?
ReplyDeleteAnd do you want to permanently change one of the original objects,
or do you want a new merged object returned?
function mergedObject(obj1, obj2, force){
for(var p in obj1) this[p]= obj1[p];
for(var p in obj2){
if(obj2.hasOwnProperty(p)){
if(force || this[p]=== undefined) this[p]= obj2[p];
else{
n= 2;
while(this[p+n]!== undefined)++n;
this[p+n]= obj2[p];
}
}
}
}
Underscore also has an extend method:
ReplyDeleteCopy all of the properties in the source objects over to the
destination object. It's in-order, so the last source will override
properties of the same name in previous arguments.
_.extend(destination, *sources)
_.extend({name : 'moe'}, {age : 50});
=> {name : 'moe', age : 50}
Yahoo UI (YUI) also has a helper function for this:
ReplyDeletehttp://developer.yahoo.com/yui/examples/yahoo/yahoo_merge.html
YAHOO.namespace('example');
YAHOO.example.set1 = { foo : "foo" };
YAHOO.example.set2 = { foo : "BAR", bar : "bar" };
YAHOO.example.set3 = { foo : "FOO", baz : "BAZ" };
var Ye = YAHOO.example;
var merged = YAHOO.lang.merge(Ye.set1, Ye.set2, Ye.set3);
Keep it simple...
ReplyDeletefunction mergeArray(array1,array2) {
for(item in array1) {
array2[item] = array1[item];
}
return array2;
}