Working with Arrays in Javascript

Given this:

var array1 = ['Earl', 'John', 'Shelia', 'Lenny']

… you can get the index of "Lenny" like this:

array1.indexOf('Lenny');  //3

So you simply need to plug that into the other array:

array2[array1.indexOf('Lenny')] //99

Snippet

var array1 = ['Earl', 'John', 'Shelia', 'Lenny'],
    array2 = [85,92,87,99]

console.log(array2[array1.indexOf('Lenny')]); //99

The data structure that you are looking for is a bidirectional map. Description from Wikipedia:

In computer science, a bidirectional map, or hash bag, is an associative data structure in which the (key, value) pairs form a one-to-one correspondence. Thus the binary relation is functional in each direction: value can also act as a key to key. A pair (a, b) thus provides a unique coupling between a and b so that b can be found when a is used as a key and a can be found when b is used as a key.

Mathematically, a bidirectional map between keys and values is equivalent to a pair of functions:

1. A function f from keys to values (i.e. a -> b).
2. A function g from values to keys (i.e. b -> a).

In addition, there are two constraints imposed on bidirectional maps:

1. Given any key x the constraint g (f x) = x must be satisfied.
2. Given any value y the constraint f (g y) = y must be satisfied.

Therefore, Bimap(a, b) = (a -> b, b -> a).

Alternatively, a bidirectional map can be represented as a pair of maps or associative arrays:

Since Map(a, b) = a -> b, therefore Bimap(a, b) = (Map(a, b), Map(b, a)).

Internally, an associative array could be represented as either a pair of lists (i.e. ([a], [b])) or a list of pairs (i.e. [(a, b)]) or hash tables or any other suitable data structure.

Let's implement a bidirectional map data structure using hash tables internally for efficiency:

function Bimap(keys, vals) {
    var length = Math.min(keys.length, vals.length);

    var valMap = this.lookupVal = Object.create(null);
    var keyMap = this.lookupKey = Object.create(null);

    for (var i = 0; i < length; i++) {
        var key = keys[i];
        var val = vals[i];

        valMap[key] = val;
        keyMap[val] = key;
    }
}

You can use it as follows:

var bimap = new Bimap(["Earl", "John", "Shelia", "Lenny"], [85, 92, 87, 99]);

bimap.lookupVal["Lenny"]; // 99
bimap.lookupKey[99]; // "Lenny"

You can also add new key value pairs to the bidirectional map as follows:

Bimap.prototype.insert = function (keys, vals) {
    var length = Math.min(keys.length, vals.length);

    var valMap = this.lookupVal;
    var keyMap = this.lookupKey;

    for (var i = 0; i < length; i++) {
        var key = keys[i];
        var val = vals[i];

        valMap[key] = val;
        keyMap[val] = key;
    }
};

You would use it as follows:

bimap.insert(["Jane"], [96]);

bimap.lookupVal["Jane"]; // 96
bimap.lookupKey[96]; // "Jane"

You can summarize bidirectional maps (such as finding min/max values, etc.) using reduce:

Bimap.prototype.reduceVals = function (inductive, basis) {
    var valMap = this.lookupVal, undefined;

    return basis === undefined ?
        Object.keys(valMap).reduce(callback) :
        Object.keys(valMap).reduce(callback, basis);

    function callback(proof, key) {
        return inductive(proof, valMap[key]);
    }
};

For example:

bimap.lookupKey[bimap.reduceVals(Math.min)]; // "Earl"
bimap.lookupKey[bimap.reduceVals(Math.max)]; // "Lenny"

Finally, most JavaScript engines now natively support the Map data structure. Hence, you can implement Bimap in terms of that instead.

You can create object of array in javascript like this

[{Name : "Test" , Score : 25},{Name : "Test Two" , Score : 35}]

The best way to do this is by using either associative arrays or multi-dimensional arrays. I would suggest taking a look at this tutorial: www.w3schools.com/js/js_arrays.asp

If I understand your question correctly, you want to be able to match a name with a score in two different arrays. To do this, let's say they give you Lenny, first by using a for loop, you can loop through the first array, and look for his name, while keeping count on which index you're on. The code would look like

int index = 0;
for(; index < array1.size(); index++)

When you find his name, just use that index that you found like array2[index] and you'll have your answer.