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Optimize mapObj #202

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Merged
xymostech merged 1 commit into from
Mar 7, 2017
Merged

Optimize mapObj #202

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19 changes: 9 additions & 10 deletions src/util.js
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Original file line number Diff line number Diff line change
Expand Up @@ -10,19 +10,18 @@ type ObjectMap = { [id:string]: any };
// {K1: V1, K2: V2, ...} -> [[K1, V1], [K2, V2]]
export const objectToPairs = (obj /* : ObjectMap */) /* : Pairs */ => Object.keys(obj).map(key => [key, obj[key]]);

// [[K1, V1], [K2, V2]] -> {K1: V1, K2: V2, ...}
const pairsToObject = (pairs /* : Pairs */) /* : ObjectMap */ => {
const result = {};
pairs.forEach(([key, val]) => {
result[key] = val;
});
return result;
};

export const mapObj = (
obj /* : ObjectMap */,
fn /* : PairsMapper */
) /* : ObjectMap */ => pairsToObject(objectToPairs(obj).map(fn))
) /* : ObjectMap */ => {
const keys = Object.keys(obj);
const mappedObj = {};
for (let i = 0; i < keys.length; i += 1) {
const [newKey, newValue] = fn([keys[i], obj[keys[i]]]);
mappedObj[newKey] = newValue;
}
return mappedObj;
}

// Flattens an array one level
// [[A], [B, C, [D]]] -> [A, B, C, [D]]
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