Javascript - Array with Boolean Keys?

Question

I'm relatively new to Javascript, and there's probably just a trick I'm not familiar with, but how can I assign boolean values to Array keys?

What's happening:

var test = new Array();
test[false] = "asdf";
test['false'] = "fdsa";

Object.keys(test); // Yield [ "false" ]
Object.keys(test).length; // Yield 1

What I want to happen:

var test = new Array();

//Some stuff

Object.keys(test); // Yield [ "false" , false ]
Object.keys(test).length; // Yield 2

Solution 1

You can't use arbitrary indexes in an array, but you can use an object literal to (sort of) accomplish what you're after:

var test = {};
test[false] = "asdf";
test['false'] = "fdsa";

However it should be noted that object properties must be strings (or types that can be converted to strings). Using a boolean primitive will just end up in creating an object property named 'false'.

test[false] === test['false'] === test.false

This is why your first example's Object.keys().length call returns just 1.

For an excellent getting started guide on objects in JavaScript, I would recommend MDN's Working with objects.

Solution 2

Arrays in Javascript aren't associative, so you cannot assign values to keys in them.

var test = [];
test.push(true);  // [true]
test.push(false); // [true, false]

You're interested in an Object!

var test    = {};
test[true]  = "Success!";
test[false] = "Sadness";  // {'false': "Sadness", 'true': "Success"}

Solution 3

you could also reverse the answer above such as

let test = [true];

console.log(typeof test);

// Output: Object True

Solution 4

Javascript arrays are only number index based. You could use 0 and 1 as keys (although I can't think of a case where you need boolean keys). myArr[0] = "mapped from false"; myArr[1] = "mapped from true";

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Comments

[Admin]

This is good to know. Maybe I'm just too spoiled for working mainly in PHP for the last year. I don't suppose I could have an array object with numeric and "associative" keys at the same time, could I? Basically, I need an array that holds single-level arrays, and if a user belongs to a certain group, a key is created in the upper-array to hold the lower-array of user information within that group, and if they're not a part of a group, they need to default to a "blank" group. The problem is that the group could be named anything, so I'd like this "blank" key to not be a string.

[Andrew Whitaker]

You can name object properties integers (var obj = { }; obj[1] = 'foo' }). Typically you would use an object and then create a property of that object that's an array: var obj = { }; obj.ArrayProp = [];. Hope that helps...

[Admin]

Thank you. People like you are the reason I love this site.