JavaScript 中以字母为键的关联数组

Question

I am looking to create a JavaScript object (associative array) with alphabets as keys. What is the best way to accomplish this?

Example -

obj[a] = 'somevalue'
obj[b] = 'somevalue' 
...
obj[z]= 'some value'

Assigning alphabets as keys dynamically.

Answer 1

Here's a quick and lazy way to create the object:

var a = 97;
var charArray = {};
for (var i = 0; i<26; i++)
    charArray[String.fromCharCode(a + i)] = String.fromCharCode(a + i);

console.log(charArray);

http://jsfiddle.net/V2B7S/

Answer 2

var obj = { };
obj['A'] = 'letter A';
obj['B'] = 'letter B';
obj['C'] = 'letter C';

or:

var obj = [ ];
obj['A'] = 'letter A';
obj['B'] = 'letter B';
obj['C'] = 'letter C';

and then:

alert(obj.B);

or the equivalent:

alert(obj['B']);

I would use the { } syntax for non-integer based indexes though. Why? Because there are some real gotchas when you use [ ] with non-integer indexes, like this one:

var obj = [ ];
obj['A'] = 'letter A';
obj['B'] = 'letter B';
obj['C'] = 'letter C';
alert(obj.length);

Guess what will be printed? Yes, you guessed it: 0.

Answer 3

var hash = {};
hash["abcdefghijklmnopqrstuvwxyz"] = "something";
hash["בגדהוזחטיךכלםמןנסעףפץצקרשת"] = "something else";
hash["АБВГДЕЖЅZЗИІКЛМНОПРСТȢѸФХѾЦЧШЩЪꙐЬѢꙖѤЮѦѪѨѬѠѺѮѰѲѴ"] = "something else";

Answer 4

First create an array of letters using the trick Thack Mai used :

var associateArray = []  
for (i = 65; i <= 90; i++) {
    associateArray[i-65] = String.fromCharCode(i).toLowerCase()
}

Then map values to any of the letters you want to map values to

associateArray['a'] = 1
associateArray['b'] = 2

This creates the type of object used in browsers for CSSStyleDeclaration. It can be iterated over like so

for (var i = 0; i < associateArray.length; i++) {
    console.log(associateArray[associateArray[i]])
}

Answer 5

You can use reduce to create an associative array:

 const dict = Array.from(new Array(26)) .reduce((p, c, i) => (p[String.fromCharCode(i + 97)] = i, p), {}) console.log(dict)

Answer 6

function range( start, limit ){
    var assoc_array = {};
    var step = 1;
    var DEFAULT_VALUE = "some value";
    step *= limit.charCodeAt(0) - start.charCodeAt(0) > 0 ? 1:-1;
    while( start !== limit ){
        assoc_array[ start ] = DEFAULT_VALUE;
        start = String.fromCharCode(start.charCodeAt(0)+step);
    }
    assoc_array[ limit ] = DEFAULT_VALUE;
    return assoc_array;
}
//Usage examples
var alphabet_array = range('a','z');
var reverse_alphabet_array = range('z','a');

DEMO