[Create an Index Object from an Array of values, based on a passed attribute's value] #JavaScript #Array

index.js

// Creates a Dictionary / Index Object for all the objects based on the passed attribute value.

/**
 * Create an object with keys based on a passed attribute within the array of values
 * @param {[*]} objects - array of objects
 * @param {string} attributeName - the attribute name
 * @return {*}
 */
var indexByAttribute = function indexByAttribute ( objects, attributeName ) {
    return (objects||[])
        .reduce(function reducer(previousValue,currentValue,currentIndex,array) {
            if( currentValue && previousValue.hasOwnProperty( currentValue[attributeName] ) ) {
                // previousValue[ currentValue[attributeName] ].push( currentValue );
                throw new Error('non unique value encountered in objects')
            } else if ( currentValue ) {
                previousValue[ currentValue[attributeName] ] = currentValue ;
            }
            return previousValue
        }, {});
}

let x = {
    "keys": [
        {
            "kid": "747527d1-12f6-4e58-a7dd-394dd9161a99",
            "kty": "RSA",
            "alg": "RS256",
            "use": "sig",
            "n": "2898e1e0-cebf-44e0-bc20-8d5b868e170b-fae7028a-dbae-483a-9849-390ca82d6282-d7910462-c128-4c7d-88ba-ca48efee0839",
            "e": "AQAB"
        },
        {
            "kid": "c9567bf8-5684-40fc-bc24-858d493042b8",
            "kty": "RSA",
            "alg": "RS256",
            "use": "sig",
            "n": "b3236ed7-75c3-4e78-9fd9-b464060469b7-bd04a9e6-78d5-4f40-b8da-19c879d5d51a-d7910462-c128-4c7d-88ba-ca48efee0839",
            "e": "AQAB"
        },
    ]
}

console.log(JSON.stringify( indexByAttribute( x.keys, 'kid' ) , null, 4));
/**
 {
    "747527d1-12f6-4e58-a7dd-394dd9161a99": {
        "kid": "747527d1-12f6-4e58-a7dd-394dd9161a99",
        "kty": "RSA",
        "alg": "RS256",
        "use": "sig",
        "n": "2898e1e0-cebf-44e0-bc20-8d5b868e170b-fae7028a-dbae-483a-9849-390ca82d6282-d7910462-c128-4c7d-88ba-ca48efee0839",
        "e": "AQAB"
    },
    "c9567bf8-5684-40fc-bc24-858d493042b8": {
        "kid": "c9567bf8-5684-40fc-bc24-858d493042b8",
        "kty": "RSA",
        "alg": "RS256",
        "use": "sig",
        "n": "b3236ed7-75c3-4e78-9fd9-b464060469b7-bd04a9e6-78d5-4f40-b8da-19c879d5d51a-d7910462-c128-4c7d-88ba-ca48efee0839",
        "e": "AQAB"
    }
}
 */