Javascript Enum To Corresponding String Value

Do you actually need the numeric values at all? If not then you could use something like this:

var TEST_ERROR  = {    SUCCESS  : 'Success',    FAIL     : 'Fail',    ID_ERROR : 'ID Error'};

Not quite optimal, but the cleanest you can get without pre-computing the reverse dictionary (and besides, this shouldn't be too much of an issue if you only have a few enumeration values):

function string_of_enum(enum,value) {  for (var k in enum) if (enum[k] == value) return k;  return null;}

For TypeScript, there is a simpler solution(Please ignore my answer if you stick with JS):

export enum Direction {    none,    left = 1,    right = 2,    top = 4,    bottom = 8}export namespace Direction {    export function toString(dir: Direction): string {        return Direction[dir];    }    export function fromString(dir: string): Direction {        return (Direction as any)[dir];    }}console.log("Direction.toString(Direction.top) = " + Direction.toString(Direction.top));// Direction.toString(Direction.top) = topconsole.log('Direction.fromString("top") = ' + Direction.fromString("top"));// Direction.fromString("top") = 4console.log('Direction.fromString("xxx") = ' + Direction.fromString("unknown"));// Direction.fromString("xxx") = undefined

Because the enumeration type is compiled into an object(dictionary).You don't need a loop to find the corresponding value.

enum Direction {    left,    right}

is compiled into:

{    left: 0    right: 1    0: "left",    1: "right"}