javascript搜索数组以获取数组索引？

Question

Say I have:

a=[[1,2],[3,4],[5,6]]

Is this wrong?

a.indexOf([1,2])

Why -1?

Answer 1

Because [1,2] == [1,2] is false

There is no equality of different instances of javascript objects.

From the MDN on == :

If both operands are objects, then JavaScript compares internal references which are equal when operands refer to the same object in memory.

You could build your own function to look for an array in an array, but in this case, as you would have to check all elements of the internal arrays (or build a hash code), this won't be fast. You'd better avoid this kind of search.

Answer 2

You CANNOT compare ARRAYS in JAVASCRIPT!

JavaScript Arrays are essentially inherited from objects when you check equality condition the internal references of these tow objects are different which returns -1 despite if all the elements are same

So when you call .indexOf it will compare arrays which will fail and hence you get -1

You need to build your own function which deeply checks if the Array and its sub arrays are equal or you can use some libraries like _.js