Object map in JavaScript

Question

I want to make a map object that key is object.

But, JavaScript only allows string as a hash key. (at least before ECMAScript6 comes?)

So, I tried to write auxiliary functions to emulate, hash-ish (but actually linear search). Are there any suggestions on improvement?

var tabInfo = {};
var tabInfoKey = 0;
function getTabInfoItem(tab) {
 console.log("getTabInfoItem", tab);
 for(var key in tabInfo) {
 if(tabInfo[key].tab === tab) {
 return tabInfo[key].info;
 }
 }
}
function setTabInfoItem(tab, info) {
 console.log("setTabInfoItem", tab, info);
 for(var key in tabInfo) {
 if(tabInfo[key].tab === tab) {
 tabInfo[key] = {
 tab: tab,
 info: info
 };
 return;
 }
 }
 tabInfoKey++;
 tabInfo[tabInfoKey] = {
 tab: tab,
 info: info
 };
}
function deleteTabInfoItem(tab) {
 console.log("deleteInfoItem", tab);
 for(var key in tabInfo) {
 if(tabInfo[key].tab === tab) {
 delete tabInfo[key];
 return;
 }
 }
}

• Florian Margaine: Why don't you simply use a shim?

Answer 1

I can't see a good use for this, but nonetheless:

• Since you treat tabInfo as a list, why not have it be an array, this way you don't need tabInfoKey and you can use push instead. Arrays are objects too.
• Don't use console.log for production code
• tab is a terrible name, go for either the Spartan o or object
• info is an unfortunate name, perhaps value ?
• tabInfo is also meh, perhaps objectMap ?
• you should have a constructor for this!

Something like this incorporates my feedback:

function ObjectMap() {
 this.entries = [];
}
ObjectMap.prototype.get = function( object ) {
 for( var i = 0 , length = this.entries.length ; i < length ; i++ ){
 if( this.entries[i].object === object ){
 return this.entries[i].value;
 }
 }
}
ObjectMap.prototype.set = function( object, value ) {
 //If we can find it, update it
 for( var i = 0 , length = this.entries.length ; i < length ; i++ ){
 if( this.entries[i].object === object ){
 this.entries[i].value = value;
 return;
 }
 }
 //Otherwise, generate an entry 
 this.entries.push( { object : object , value : value } );
}
ObjectMap.prototype.remove = function( object ) {
 for( var i = 0 , length = this.entries.length ; i < length ; i++ ){
 if( this.entries[i].object === object ){
 this.entries.splice( i , 1 );
 return;
 }
 }
}

You can then

o = new ObjectMap();
o.set( o , "123" );
o.get( o ); //Gives "123"
o.remove( o );
o.get( o ); //Gives nothing

Furthermore you should consider whether you want to allow function chaining, right now none of these functions return anything and it seems a shame.