[英]JavaScript 2dimensional array
I have following 我有以下
var arrayT = new Array();
arrayT['one'] = arrayT['two'] = new Array();
arrayT['one']['a'] = arrayT['one']['b'] = '';
arrayT['two'] = arrayT['one'];
arrayT['two']['a'] = 'test';
console.log(arrayT);
In console I have 在控制台中,我有
[one][a]='test'
[one][b]=''
[two][a]='test'
[two][b]=''
Why? 为什么?
The line 线
arrayT['one'] = arrayT['two'] = new Array();
creates a single shared array object . 创建一个共享数组对象 。 Each "inner" array in your two-dimensional array is really just a reference to the same object, so altering one "inner" array will necessarily affect the other in the exact same way.
二维数组中的每个“内部”数组实际上只是对同一对象的引用,因此更改一个“内部”数组将必然以完全相同的方式影响另一个。
Instead, create two separate arrays: 而是创建两个单独的数组:
arrayT['one'] = new Array();
arrayT['two'] = new Array();
Futhermore , even if you implement that change, the line: 此外 ,即使您实施了该更改,该行也会:
arrayT['two'] = arrayT['one'];
will create the same problem -- arrayT['two']
and arrayT['one']
will point to the same object, possibly causing future problems of a similar nature (eg, altering arrayT['two']['a']
on the next line will alter arrayT['one']['a']
, since they point to the same object). 会产生相同的问题
arrayT['two']
和arrayT['one']
将指向同一对象,可能会导致类似性质的未来问题(例如,更改arrayT['two']['a']
在下一行将更改arrayT['one']['a']
,因为它们指向同一对象)。
arrayT['one']
and arrayT['two']
are the same array, any change you make to one will affect the other. arrayT['one']
和arrayT['two']
是同一数组,您对其中一个所做的任何更改都会影响另一个。
To fix this, create separate arrays: 要解决此问题,请创建单独的数组:
arrayT['one'] = new Array();
arrayT['two'] = new Array();
This issue of multiple references to the same array happens when you use arrayT['one'] = arrayT['two'] = new Array()
, but arrayT['two'] = arrayT['one']
will create the same issue. 当您使用
arrayT['one'] = arrayT['two'] = new Array()
,会发生对同一数组的多个引用的问题,但是arrayT['two'] = arrayT['one']
将创建相同的arrayT['two'] = arrayT['one']
问题。 To make arrayT['two']
a copy of arrayT['one']
you should use the following: 要使
arrayT['two']
成为arrayT['one']
的副本,您应该使用以下命令:
arrayT['two'] = arrayT['one'].slice();
While apsillers is right with his answer, a more accurate replacement would be to simply write arrayT['two'] = arrayT['one'].slice(0)
leaving out the assignment to arrayT['two']
in line 2. Note, that this is only a shallow copy. 虽然apsillers的回答是正确的,但更准确的替代方法是只写
arrayT['two'] = arrayT['one'].slice(0)
而arrayT['two']
第2行中对arrayT['two']
的分配。注意,这只是一个浅表副本。 Depending on your needs you might need to do a deep copy, if you should decide to use mutable objects later. 如果您以后决定使用可变对象,则可能需要根据需要进行深度复制。
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