var myIds = [3, 4, 2];
var myObj = [
{id:1, name:'one'},
{id:2, name:'two'},
{id:3, name:'tree'},
{id:4, name:'four'}];
// need to obtain ['tree', 'four', 'two']
var idsToNames= function(ids, objects) {
var myNames = myIds.map(function(id){
// transform id to name
foreach(o in objects){
if (i.id == id)
return o.name;
}
});
return myNames;
}
Is it the optimal way to transform a id array into a name array?
First transform your object like this
var newMyObj = myObj.reduce(function(result, currentObject) {
result[currentObject.id] = currentObject.name;
return result;
}, {});
console.log(newMyObj);
// { '1': 'one', '2': 'two', '3': 'three', '4': 'four' }
You can actually create the newMyObj by iterating the array myObj, like this as well
var newMyObj = {};
for (var i = 0; i < myObj.length; i += 1) {
newMyObj[myObj[i].id] = myObj[i].name;
}
Now, you can simply iterate myIds and pick values from newMyObj, like this
console.log(myIds.map(function(id) { return newMyObj[id]; }));
// [ 'three', 'four', 'two' ]
If your environment supports ECMAScript 2015's Arrow functions, this can be written succinctly as
console.log(myIds.map((id) => newMyObj[id]));
// [ 'three', 'four', 'two' ]
By transforming your original myObj to newMyObj you will be getting constant time lookup. Otherwise you have to iterate the myObj array for every element in the myIds and runtime complexity will become O(n*m).