Does Javascript have associative arrays?

Question

Does Javascript have associative arrays? Please explain.

Answer 1

This answer is pretty much a copy-paste of my previous answer on this question.

The situation has changed in the five years since this question was asked.

Due to weak typing associative arrays can be faked in JavaScript:

>> var names = new Array();
undefined

>> names["first"] = "Dotan";
"Dotan"

>> names["last"] = "Cohen";
"Cohen"

>> for ( key in names ) { console.log(key+" "+names[key]) }
undefined
first Dotan
last Cohen

That is sometimes useful, and all browsers released since 2012 support it, but there are caveats! The array cannot be simply read back:

>> names
Array [  ]

More importantly, the array's length cannot be easily retrieved:

>> names.length
0

Therefore this is not an associative array in the sense that JavaScript would have supported it had it been intended, but rather a workaround that is often useful if for whatever reason a real JS object does not support what you need:

>> var names = {};
undefined

>> names.first = "Dotan";
"Dotan"

>> names.last = "Cohen";
"Cohen"

>> for ( key in names ) { console.log(key+" "+names[key]) }
undefined
first Dotan
last Cohen

>> names
Object { first: "Dotan", last: "Cohen" }

>> Object.keys(names).length
2